IN 


John  Sv/ett 


METHODS  OF  STUDIU! 


NATURAL    HISTORY, 


BY  L.    AGASSIZ. 


BOSTON: 
TICKNOR    AND    FIELDS. 

1866. 


Entered  according  to  Act  of  Congress,  in  the  yeaf  1863,  by 

TICKNOR     AND     FIELDS, 
In  the  Clerk's  Office  of  the  District  Court  of  the  District  of  Massachusetts. 

EDUCATION  DEPfc 


THIRD    EDITION. 


UNIVERSITY   PRESS: 

WELCH.    BIGELOW,    AND   COMPANY, 

CAMBRI  DGE. 


PREFACE. 


THE  series  of  papers  collected  in  this  volume 
may  be  considered  as  a  complement  or  commen- 
tary to  my  "  Essay  on  Classification,"  since  I 
have  endeavored  to  present  here  in  a  more  pop- 
ular form  the  views  first  expressed  in  that  work. 
And  although  the  direct  intention  of  these  pages 
has  been,  as  their  title  indicates,  to  give  some 
general  hints  to  young  students  as  to  the  meth- 
ods by  which  scientific  truth  has  been  reached, 
including  a  general  sketch  of  the  history  of  sci- 
ence in  past  times,  yet  I  have  also  wished  to 
avail  myself  of  this  opportunity  to  enter  my  ear- 
nest protest  against  the  transmutation  theory, 
revived  of  late  with  so  much  ability,  and  so 
generally  received.  It  is  my  belief  that  natural- 
ists are  chasing  a  phantom,  in  their  search  after 
some  material  gradation  among  created  beings, 
by  which  the  whole  Animal  Kingdom  may  have 
been  derived  by  successive  development  from  a 

54-1763 


IV  PREFACE. 

single  germ,  or  from  a  few  germs  It  would 
seem,  from  the  frequency  with  which  this  notion 
is  revived,  —  ever  returning  upon  us  with  hydra- 
headed  tenacity  of  life,  and  presenting  itself 
under  a  new  form  as  soon  as  the  preceding  one 
has  been  exploded  and  set  aside,  —  that  it  has  a 
certain  fascination  for  the  human  mind.  This 
arises,  perhaps,  from  the  desire  to  explain  the 
secret  of  our  own  existence ;  to  have  some  sim- 
ple and  easy  solution  of  the  fact  that  we  live. 

I  confess  that  there  seems  to  me  to  be  a  repul- 
sive poverty  in  this  material  explanation,  that  is 
contradicted  by  the  intellectual  grandeur  of  the 
universe  ;  the  resources  of  the  Deity  cannot  be  so 
meagre,  that,  in  order  to  create  a  human  being 
endowed  with  reason,  he  must  change  a  monkey 
into  a  man.  This  is,  however,  merely  a  personal 
opinion,  and  has  no  weight  as  an  argument ;  nor 
am  I  so  uncandid  as  to  assume  that  another  may 
not  hold  an  opinion  diametrically  opposed  to  mine 
in  a  spirit  quite  as  reverential  as  my  own.  But  I 
nevertheless  insist,  that  this  theory  is  opposed  to 
the  processes  of  Nature,  as  far  as  we  have  been 
able  to  apprehend  them  ;  that  it  is  contradicted 
by  the  facts  of  Embryology  and  Paleontology, 
the  former  showing  us  norms  of  development  as 


PREFACE.  V 

distinct  and  persistent  for  each  group  as  are 
the  fossil  types  of  each  period  revealed  to  us  by 
the  latter  ;  and  that  the  experiments  upon  domes- 
ticated animals  and  cultivated  plants,  on  which 
its  adherents  base  their  views,  are  entirely  foreign 
to  the  matter  in  hand,  since  the  varieties  thus 
brought  about  by  the  fostering  care  of  man  are 
of  an  entirely  different  character  from  those  ob- 
served among  wild  species.  And  while  their 
positive  evidence  is  inapplicable,  their  negative 
evidence  is  equally  unsatisfactory,  since,  however 
long  and  frequent  the  breaks  in  the  geological  se- 
ries may  be  in  which  they  would  fain  bury  their 
transition  types,  there  are  many  points  in  the 
succession  where  the  connection  is  perfectly  dis- 
tinct and  unbroken,  and  it  is  just  at  these  points 
that  new  organic  groups  are  introduced  without 
any  intermediate  forms  to  link  them  with  the 
preceding  ones.  In  another  series  of  papers,  I 
shall  endeavor  to  show  the  futility  of  the  argu- 
ment so  far  as  it  is  founded  upon  the  r  imperfec- 
tion of  the  geological  record. 

I  would  add  one  word  upon  the  way  in  which 
this  volume  has  been  prepared,  since  it  has  some 
features  requiring  explanation,  if  not  apology. 
These  chapters  were  first  embodied  in  a  course 


VI  PREFACE. 

of  lectures  delivered  at  the  Lowell  Institute  in 
Boston,  without  any  thought  of  their  subsequent 
publication.  Notes  were,  however,  taken  of 
them  at  the  time,  and  I  very  willingly  assented 
to  the  suggestion  of  some  of  my  listeners,  that 
they  should  be  recorded  in  the  form  of  articles 
for  the  Atlantic  Monthly.  They  still  retain  some- 
thing of  the  repetition  which  is  needed  in  a 
public  course  of  scientific  lectures  in  order  to 
keep  the  connection  of  the  subjects  clearly  before 
the  mind  of  a  popular  audience.  An  attempt 
to  change  this  character  would  have  amounted 
to  writing  the  whole  course  anew,  —  a  task  for 
which  I  had  neither  time  nor  inclination.  I  have 
endeavored  to  avoid  technicalities  as  far  as  pos- 
sible in  dealing  with  subjects  many  of  which 
are  quite  unfamiliar  to  the  general  mind  ;  and  the 
closing  chapter  of  the  book,  which  has  been  in- 
corporated in  the  volume,  but  did  not  appear  in 
the  Atlantic  Monthly,  is  the  only  one  especially 
addressed  to  the  professional  naturalist. 

L.   AGASSIZ. 

NAHANT,  August  22,  1863. 


CONTENTS. 


CHAPTER   I. 

GENERAL  SKETCH  OF  THE  EARLY  PROGRESS  IN  NATURAL 


CHAPTER    II. 

NOMENCLATURE  AND   CLASSIFICATION  .          ,          .  .        16 

CHAPTER   III. 

CATEGORIES  OF   CLASSIFICATION         .          .          .          »          .          .30 

CHAPTER   IV. 

CLASSIFICATION  AND   CREATION          .          .          .          •          .          .41 

CHAPTER    V. 

DIFFERENT   VIEWS   RESPECTING   ORDERS 72 

CHAPTER    VI. 

GRADATION  AMONG   ANIMALS 84 

CHAPTER    VII. 

ANALOGOUS  TYPES        .          . 108 

CHAPTER    VIII. 

FAMILY   CHARACTERISTICS  .  .  .  .  •  .  .      109 


viii  CONTENTS. 

CHAPTER   IX. 

THE  CHARACTERS  OF  GENERA 126 

CHAPTER    X. 

SPECIES  AND   BREEDS  .          .          .^        •  •          •          •          •      134 

CHAPTER    XI. 

FORMATION   OF   CORAL   REEFS 148 

CHAPTER    XII. 

AGE  OF   CORAL  REEFS  AS  SHOWING  PERMANENCE  OF  SPECIES      176 

CHAPTER    XIII. 

HOMOLOGIES  201 

CHAPTER    XIV. 

ALTERNATE  GENERATIONS 288 

CHAPTER   XV. 

THE  OVARIAN  EGG 269 


CHAPTER    XVI. 

EMBRYOLOGY  AND   CLASSIFICATION 296 


METHODS  OF  STUDY  IN  NATURAL 
HISTORY. 


CHAPTER    I. 

GENERAL    SKETCH    OF    THE  "EARLY   PROGRESS  IN 
NATURAL  HISTORY. 

IT  is  my  intention,  in  this  series  of  papers,  to 
give  the  history  of  the  progress  in  Natural  His- 
tory from  the  beginning,  —  to  show  how  men 
first  approached  Nature,  —  how  the  facts  of  Nat- 
ural History  have  been  accumulated,  and  how 
these  facts  have  been  converted  into  science.  In 
so  doing,  I  shall  present  the  methods  followed 
in  Natural  History  on  a  wider  scale  and  with 
broader  generalizations  than  if  I  limited  myself 
to  the  study  as  it  exists  to-day.  The  history  of 
humanity,  in  its  efforts  to  understand  the  Crea- 
tion, resembles  the  development  of  any  individ- 
ual mind  engaged  in  the  same  direction.  It 
has  its  infancy,  with  the  first  recognition  of 
surrounding  objects  ;  and,  indeed,  the  early  ob- 
servers seem  to  us  like  children  in  their  first  at- 
tempts to  understand  the  world  in  which  they 


2  i    t  EARLY  PROGRESS 

i  il  '    <•  <• 

live. :  But  these  efforts,  that  appear  childish  to  us 
liowywefe  "the  first  steps  in  that  field  of  knowl- 
edge which  is  so  extensive  that  all  our  progress 
seems  only  to  show  us  how  much  is  left  to  do. 

Aristotle  is  the  representative  of  the  learning 
of  antiquity  in  Natural  Science.  The  great  mind 
of  Greece  in  his  day,  and  a  leader  in  all  the  in- 
tellectual culture  of  his  time,  he  was  especially  a 
naturalist,  and  his  work  on  Natural  History  is 
a  record  not  only  of  his  own  investigations,  but 
of  all  preceding  study  in  this  department.  It 
is  evident  that  even  then  much  had  been  done, 
and,  in  allusion  to  certain  peculiarities  of  the 
human  frame,  which  he  does  not  describe  in  full, 
he  refers  his  readers  to  familiar  works,  saying, 
that  illustrations  in  point  may  be  found  in  ana- 
tomical text-books.* 

Strange  that  in  Aristotle's  day,  two  thousand 
years  ago,  such  books  should  have  been  in  gen- 
eral use,  and  that  in  our  time  we  are  still  in 
want  of  elementary  text-books  of  Natural  His- 
tory, having  special  reference  to  the  animals  of 
our  own  country,  and  adapted  to  the  use  of 
schools.  One  fact  in  Aristotle's  "  History  of 
Animals  "  is  very  striking,  and  makes  it  diffi- 
cult for  us  to  understand  much  of  its  contents. 
It  never  occurs  to  him  that  a  time  may  come 
when  the  Greek  language  —  the  language  of  all 

*  See  Aristotle's  Zoology,  Book  I,  Chapter  XIV. 


IN  NATURAL  HISTORY.  3 

culture  and  science  in  his  time  —  would  not  be 
the  language  of  all  cultivated  men.  He  took, 
therefore,  little  pains  to  characterize  the  animals 
he  alludes  to,  otherwise  than  by  their  current 
names  ;  and  of  his  descriptions  of  their  habits 
and  peculiarities,  much  is  lost  upon  us  from 
their  local  character  and  expression.  There  is 
also  a  total  absence  of  systematic  form,  of  any 
classification  or  framework  to  express  the  divis- 
ions of  the  animal  kingdom  into  larger  or  lesser 
groups.  His  only  divisions  are  genera  and  spe- 
cies :  classes,  orders,  and  families,  as  we  under- 
stand them  now,  are  quite  foreign  to  the  Greek 
conception  of  the  animal  kingdom.  Fishes  and 
birds,  for  instance,  they  considered  as  genera, 
and  their  different  representatives  as  species. 
They  grouped  together  quadrupeds  also,  in  con- 
tradistinction to  animals  with  legs  and  wings, 
and  they  distinguished  those  that  bring  forth 
living  young  from  those  that  lay  eggs.  But 
though  a  system  of  Nature  was  not  familiar 
even  to  their  great  philosopher,  and  Aristotle 
had  not  arrived  at  the  idea  of  a  classification  on 
general  principles,  he  yet  stimulated  a  search 
into  the  closer  affinities  among  animals  by  the 
differences  he  pointed  out.  He  divided  the  ani- 
mal kingdom  into  two  groups,  which  he  called 
Enaima  and  Anaima,  or  animals  with  blood  and 
animals  without  blood.  We  must  remember, 


4  EARLY  PROGRESS 

however,  that  by  the  word  blood  he  designated 
only  the  red  fluid  circulating  in  the  higher  ani- 
mals ;  whereas  a  fluid  akin  to  blood  exists  in  all 
animals,  variously  colored  in  some,  but  colorless 
in  a  large  number  of  others. 

After  Aristotle,  a  long  period  elapsed  without 
any  addition  to  the  information  he  left  us. 
Rome  and  the  Middle  Ages  gave  us  nothing,  and 
even  Pliny  added  hardly  a  fact  to  those  that 
Aristotle  recorded.  And  though  the  great  nat- 
uralists of  the  sixteenth  century  gave  a  new 
impulse  to  this  study,  their  investigations  were 
chiefly  directed  towards  a  minute  acquaintance 
with  the  animals  they  had  an  opportunity  of 
observing,  mingled  with  commentaries  upon  the 
ancients.  Systematic  Zoology  was  but  little  ad- 
vanced by  their  efforts. 

We  must  come  down  to  the  last  century,  to 
Linnaeus,  before  we  find  the  history  taken  up 
where  Aristotle  had  left  it,  and  some  of  his  sug- 
gestions carried  out  with  new  freshness  and  vigor. 
Aristotle  had  already  distinguished  between  gen- 
era and  species ;  Linnaeus  took  hold  of  this  idea, 
and  gave  special  names  to  other  groups,  of  dif- 
ferent weight  and  value.  Besides  species  and 
genera,  he  gives  us  orders  and  classes,  —  con- 
sidering classes  the  most  comprehensive,  then 
orders,  then  genera,  then  species.  He  did  not, 
however,  represent  these  groups  as  distinguished 


IN  NATURAL  HISTORY.  5 

by  their  nature,  but  only  by  their  range ;  they 
were  still  to  him,  as  genera  and  species  had  been 
to  Aristotle,  only  larger  or  smaller  groups,  not 
founded  upon  and  limited  by  different  categories 
of  structure.  He  divided  the  animal  kingdom 
into  six  classes,  which  I  give  here,  as  we  shall 
have  occasion  to  compare  them  with  other  clas- 
sifications :  —  Mammalia,  Birds,  Reptiles,  Fishes, 
Insects,  and  Worms. 

That  this  classification  should  have  expressed 
all  that  was  known,  in  the  last  century,  of  the 
most  general  relations  among  animals,  only  shows 
how  difficult  it  is  to  generalize  on  such  a  sub- 
ject ;  nor  should  we  expect  to  find  it  an  easy  task, 
when  we  remember  the  vast  number  of  species 
(about  a  quarter  of  a  million)  already  noticed 
by  naturalists.  Linna3us  succeeded,  however,  in 
finding  a  common  character  on  which  to  unite 
most  of  his  classes  ;  but  his  definition  of  the 
class  of  Mammalia,  that  group  to  which  we  our- 
selves belong,  remained  very  imperfect.  Indeed, 
in  the  earlier  editions  of  his  classification,  he 
does  not  apply  the  name  of  Mammalia  to  this 
class,  but  calls  the  higher  animals  Quadrupedia, 
characterizing  them  as  the  animals  with  four  legs 
and  covered  with  fur  or  hair,  that  bring  forth 
living  young  and  nurse  them  with  milk.  In 
thus  admitting  external  features  as  class  char- 
acters, he  exchided  many  animals  which  by  their 


6  EABLY  PROGRESS 

mode  of  reproduction,  as  well  as  by  their  res- 
piration and  circulation,  belong  to  this  class  as 
much  as  the  Quadrupeds,  — •-  as,  for  instance,  all 
the  Cetaceans  (Whales,  Porpoises,  and  the  like), 
which,  though  they  have  not  legs,  nor  are  their 
bodies  covered  with  hair  or  fur,  yet  bring  forth 
living  young,  nurse  them  with  milk,  are  warm- 
blooded and  air-breathing.  As  more  was  learned 
of  these  animals,  there  arose  serious  discussion 
and  criticism  among  contemporary  naturalists 
respecting  the  classification  of  Linnaeus,  all  of 
which  led  to  a  clearer  insight  into  the  true  re- 
lations among  animals.  Linnaeus  himself,  in  his 
last  edition  of  the  "  Systema  Naturae,"  shows  us 
what  important  progress  he  had  made  since  he 
first  announced  his  views ;  for  he  there  substi- 
tutes for  the  name  of  Quadrupedia  that  of  Mam- 
malia, including  among  them  the  Whales,  which 
he  characterizes  as  air-breathing,  warm-blooded, 
and  bringing  forth  living  young  which  they  nurse 
with  milk.  Thus  the  very  deficiencies  of  his 
classification  stimulated  naturalists  to  new  criti- 
cism and  investigation  into  the  true  limits  of 
classes,  and  led  to  the  recognition  of  one  most 
important  principle,  —  that  such  groups  are 
founded,  not  on  external  appearance,  but  on 
internal  structure,  and  that  internal  structure, 
therefore,  is  the  thing  to  be  studied.  The  group 
of  Quadrupeds  was  not  the  only  defective  one 


IN  NATURAL  HISTORY.  7 

in  this  classification  of  Linna3us ;  his  class  of 
Worms,  also,  was  most  heterogeneous,  for  he 
included  among  them  Shell-Fishes,  Slugs,  Star- 
Fishes,  Sea-Urchins,  Corals,  and  other  animals 
that  bear  no  relation  whatever  to  the  class  of 
Worms  as  now  defined. 

But  whatever  its  defects,  the  classification  of 
Linnaeus  was  the  first  attempt  at  grouping  ani- 
mals together  according  to  certain  common  struc- 
tural characters.  His  followers  and  pupils  en- 
gaged at  once  in  a  scrutiny  of  the  differences 
and  similarities  among  animals,  which  soon  led 
to  a  great  increase  in  the  number  of  classes ;  in- 
stead of  six,  there  were  presently  nine,  twelve, 
and  more.  But  till  Cuvier's  time  there  was  no 
great  principle  of  classification.  Facts  were  ac- 
cumulated and  more  or  less  systematized,  but 
they  were  not  yet  arranged  according  to  law ; 
the  principle  was  still  wanting  by  which  to  gen- 
eralize them  and  give  meaning  and  vitality  to  the 
whole.  It  was  Cuvier  who  found  the  key.  He 
himself  tells  us  how  he  first  began,  in  his  investi- 
gations upon  the  internal  organization  of  animals, 
to  use  his  dissections  with  reference  to  finding  the 
true  relations  between  animals,  and  how  ever 
after  his  knowledge  of  anatomy  assisted  him  in 
his  classifications,  while  his  classifications  threw 
new  light  again  on  his  anatomical  investigations, 
—  each  science  thus  helping  to  fertilize  the  other. 


8  EARLY  PROGRESS 

He  was  not  one  of  those  superficial  observers 
who  are  in  haste  to  announce  every  new  fact  that 
they  chance  to  find,  and  his  first  paper  *  special- 
ly devoted  to  classification  gave  to  the  world  the 
ripe  fruit  of  years  of  study.  This  was  followed 
by  his  great  work,  "Lef  Regne  Animal."  He 
said  that  animals  were  united  in  their  most 
comprehensive  groups,  not  on  special  characters, 
but  on  different  plans  of  structure,  — •  moulds,  he 
called  them,  in  which  all  animals  had  been  cast. 
He  tells  us  this  in  such  admirable  language,  that 
I  must,  to  do  justice  to  his  thought,  give  it  in  his 
own  words: — 

"  Si  Ton  consid£re  le  rSgne  animal  d'aprSs  les 
principes  que  nous  venons  de  poser  en  se  d£bar- 
rassant  des  prejuge*s  e'tablis  sur  les  divisions  an- 
ciennement  admises,  en  n'ayant  e*gard  qu'a  1'or- 
ganisation  et  a  la  nature  des  animaux,  et  non 
pas  a  leur  grandeur,  a  leur  utilite*,  au  plus  ou 
moins  de  connaissance  que  nous  en  avons,  ni  a 
toutes  les  autres  circonstances  accessoires,  on 
trouvera  qu'il  existe  quatre  formes  principales, 
quatre  plans  g£n£raux,  si  Ton  peut  s'exprimer 
ainsi,  d'aprete  lesquels  tous  les  animaux  semblent 
avoir  £t6  modeled,  et  dont  les  divisions  ulte*rieures, 
de  quelque  titre  que  les  naturalistes  les  aient  de- 
core*es,  ne  sont  que  des  modifications  assez  legeres, 

*  "  Sur  un  nouveau  rapprochement  &  etablir  entre  les  Classes 
qui  composent  le  Regne  Animal."  —  Am.' Mas.,  Vol.  XIX. 


IN  NATUEAL   HISTORY.  C 

fondles  sur  le  deVeloppement  ou  1'addition  de 
quelques  parties,  qui  ne  changent  rien  a  Pessence 
du  plan."* 

The  value  of  this  principle  was  soon  tested  by 
its  application  to  facts  already  known,  and  it  was 
found  that  animals  whose  affinities  had  been 
questionable  before  were  now  at  once  referred 
to  their  true  relations  with  other  animals  by  as- 
certaining whether  they  were  built  on  one  or 
another  of  these  plans.  Of  such  plans  or  struc- 
tural conceptions  Cuvier  found  in  the  whole  ani- 
mal kingdom  only  four,  which  he  called  Verte- 
brates, Mollusks,  Articulates,  and  Radiates. 

With  this  new  principle  as  the  basis  of  investi- 
gation, it  was  no  longer  enough  for  the  naturalist 
^to  know  a  certain  amount  of  features  character- 
istic of  a  certain  number  of  animals,  —  he  must 
penetrate  deep  enough  into  their  organization  to 

*  If  we  consider  the  animal  kingdom  according  to  the  princi- 
ples advanced  above,  —  freehig  ourselves  at  the  same  time  from 
prejudices  founded  on  previously  established  divisions,  and  look- 
ing at  animals  only  with  reference  to  their  nature  and  or- 
ganization, excluding  their  size,  their  utility,  our  greater  or  less 
familiarity  with  them,  and  all  other  accessory  circumstances,  — 
we  shall  find  that  there  exist  four  principal  forms,  four  general 
plans,  if  we  may  so  express  it,  in  accordance  with  which  all 
animals  seem  to  have  been  modelled,  and  the  ulterior  divisions 
of  which,  by  whatever  title  naturalists  may  have  dignified  them, 
are  only  comparatively  light  modifications,  founded  on  the  de- 
velopment or  the  addition  of  some  parts  not  affecting  the  essen- 
tial elements  of  the  plan. 


10  EARLY   PROGRESS 

find  the  secret  of  their  internal  structure.  Till 
he  can  do  this,  he  is  like  the  traveller  in  a  strange 
city,  who  looks  on  the  exterior  of  edifices  entirely 
new  to  him,  but  knows  nothing  of  the  plan  of 
their  internal  architecture.  To  be  able  to  read 
in  the  finished  structure  the  plan  on  which  the 
whole  is  built  is  now  essential  to  every  naturalist. 
Each  of  these  plans  may  be  stated  in  the  most 
general  terms.  In  the  Vertebrates  there  is  a 
vertebral  column  terminating  in  a  prominent 
head  ;  this  column  has  an  arch  above  and  an 
arch  below,  forming  a  double  internal  cavity. 
The  parts  are  symmetrically  arranged  on  either 
side  of  the  longitudinal  axis  of  the  body.  In  the 
Mollusks,  also,  the  parts  are  arranged  according 
to  a  bilateral  symmetry  on  either  side  of  the  body, 
but  the  body  has  but  one  cavity,  and  is  a  soft, 
concentrated  mass,  without  a  distinct  individual- 
ization  of  parts.  In  the  Articulates  there  is  but 
one  cavity,  and  the  parts  are  here  again  arranged 
on  either  side  of  the  longitudinal  axis,  but  in 
these  animals  the  whole  body  is  divided  from  end 
to  end  into  transverse  rings  or  joints  movable 
upon  each  other.  In  the  Radiates  we  lose  sight 
of  the  bilateral  symmetry  so  prevalent  in  the 
other  three,  except  as  a  very  subordinate  element 
of  structure ;  the  plan  of  this  lowest  type  is  an 
organic  sphere,  in  which  all  parts  bear  definite 
relations  to  a  vertical  axis. 


IN  NATUEAL  HISTORY.  11 

It  is  not  upon  any  special  features,  then,  that 
these  largest  divisions  of  the  animal  kingdom  are 
based,  but  simply  upon  the  general  structural 
idea.  Striking  as  this  statement  was,  it  was  cold- 
ly received  at  first  by  contemporary  naturalists : 
they  could  hardly  grasp  Cuvier's  wide  generaliza- 
tions, and  perhaps  there  was  also  some  jealousy 
of  the  grandeur  of  his  views.  Whatever  the 
cause,  his  principle  of  classification  was  not  fully 
appreciated  ;  but  it  opened  a  new  road  for  study, 
and  gave  us  the  key-note  to  the  natural  affinities 
among  animals.  Lamarck,  his  contemporary, 
not  recognizing  the  truth  of  this  principle,  dis- 
tributed the  animal  kingdom  into  two  great  di- 
visions, which  he  calls  Vertebrates  and  Inverte- 
brates. Ehrenberg  also,  at  a  later  period,  an- 
nounced another  division  under  two  heads, — 
those  with  a  continuous  solid  nervous  centre, 
and  those  with  merely  scattered  nervous  swell- 
ings.* But  there  was  no  real  progress  in  either  of 
these  latter  classifications,  so  far  as  the  primary 
divisions  are  concerned ;  for  they  correspond  to 
the  old  division  of  Aristotle,  under  the  head  of 
animals  with  or  without  blood,  the  Enaima  and 
Anaima. 

This   coincidence  between   systems  based  on 

*  For  more  details  upon  the  systems  of  Zoology,  see  Agassiz's 
Essay  on  Classification  in  his  "Contributions  to  the  Natural 
History  of  the  United  States,"  Vol.  I. ;  also  printed  separately. 


12  EAKLY    PKOGKESS 

different  foundations  may  teach  us  that  every 
structural  combination  includes  certain  inherent 
necessities  which  will  bring  animals  together  on 
whatever  set  of  features  we  try  to  classify  them  ; 
so  that  the  division  of  Aristotle,  founded  on  the 
circulating  fluids,  or  that  of  Lamarck,  founded  on 
the  absence  or  presence  of  a  backbone,  or  that  of 
Ehrenberg,  founded  on  the  differences  of  the  ner- 
vous system,  covers  the  same  ground.  Lamarck 
attempted  also  to  make  the  faculties  of  animals  a 
basis  for  division  among  them.  But  our  knowl- 
edge of  the  psychology  of  animals  is  still  too 
imperfect  to  justify  any  such  use  of  it.  His 
divisions  into  Apathetic,  Sensitive,  and  Intelligent 
animals  are  entirely  theoretical.  He  places,  for 
instance,  Fishes  and  Keptiles  among  the  Intelli- 
gent animals,  as  distinguished  from  Crustacea 
and  Insects,  which  he  refers  to  the  second  division. 
But  one  would  be  puzzled  to  say  how  the  former 
manifest  more  intelligence  than  the  latter,  or  why 
the  latter  should  be  placed  among  the  Sensitive 
animals.  Again,  some  of  the  animals  that  he 
calls  Apathetic  have  been  proved  by  later  investi- 
gators to  show  an  affection  and  care  for  their 
young,  seemingly  quite  inconsistent  with  the  epi- 
thet he  has  applied  to  them.  In  fact,  we  know 
so  little  of  the  faculties  of  animals  that  any  classi- 
fication based  upon  our  present  information  about 
them  must  be  very  imperfect. 


IN  NATUKAL  HISTOKY.  13 

Many  modifications  of  Cuvier's  great  divisions 
have  been  attempted  ;  but  though  some  improve- 
ments have  been  made  in  the  details  of  hfs 
classification,  all  departures  from  its  great  funda- 
mental principle  are  errors,  and  do  but  lead  us 
away  from  the  recognition  of  the  true  affini- 
ties among  animals.  Some  naturalists,  for  in- 
stance, have  divided  off  a  part  of  the  Radiates 
and  Articulates,  insisting  upon  some  special  fea- 
tures of  structure,  and  mistaking  these  for  the 
more  important  and  general  characteristics  of 
their  respective  plans.  Subsequent  investiga- 
tions have  shown  these  would-be  improvements 
to  be  retrograde  movements,  only  proving  more 
clearly  that  Cuvier  detected  in  his  four  plans 
all  the  great  structural  ideas  on  which  the  vast 
variety  of  animals  is  founded.  This  result  is 
of  greater  importance  than  may  at  first  appear. 
Upon  it  depends  the  question,  whether  all  such 
classifications  represent  merely  individual  im- 
pressions and  opinions  of  men,  or  whether  there 
is  really  something  in  Nature  that  presses  upon 
us  certain  divisions  among  animals,  certain  affin- 
ities, certain  limitations,  founded  upon  essen- 
tial principles  of  organization.  Are  our  systems 
the  inventions  of  naturalists,  or  only  their  read- 
ing of  the  Book  of  Nature  ?  and  can  that  book 
have  more  than  one  reading  ?  If  these  clas- 
sifications are  not  mere  inventions,  if  they  are 


14        EARLY  PEOGRESS  IN  NATURAL  HISTORY. 

not  an  attempt  to  classify  for  our  own  con- 
venience the  objects  we  study,  then  they  are 
thoughts  which,  whether  we  detect  them  or  not, 
are  expressed  in  Nature,  —  then  Nature  is  the 
work  of  thought,  the  production  of  intelligence, 
carried  out  according  to  plan,  therefore  premedi- 
tated, —  and  in  our  study  of  natural  objects  we 
are  approaching  the  thoughts  of  the  Creator, 
reading  his  conceptions,  interpreting  a  system 
that  is  his  and  not  ours. 

All  the  divergence  from  the  simplicity  and 
grandeur  of  the  division  of  the  animal  kingdom 
first  recognized  by  Cuvier  arises  from  an  ina- 
bility to  distinguish  between  the  essential  fea- 
tures of  a  plan  and  its  various  modes  of  execu- 
tion. We  allow  the  details  to  shut  out  the  plan 
itself,  which  exists  quite  independent  of  special 
forms.  I  hope  we  shall  find  a  meaning  in  all 
these  plans  that  will  prove  them  to  be  the  parts 
of  one  great  conception  and  the  work  of  one 
Mind. 


NOMENCLATIVE  AND   CLASSIFICATION.  15 


CHAPTER  II. 

NOMENCLATURE  AND  CLASSIFICATION. 

PROCEEDING  upon  the  view  that  there  is  a  close 
analogy  between  the  way  in  which  every  individ- 
ual student  penetrates  into  Nature  and  the  pro- 
gress of  science  as  a  whole  in  the  history  of  hu- 
manity, I  continue  my  sketch  of  the  successive 
steps  that  have  led  to  our  present  state  of  knowl- 
edge. I  began  with  Aristotle,  and  showed  that 
this  great  philosopher,  though  he  prepared  a 
digest  of  all  the  knowledge  belonging  to  his 
time,  yet  did  not  feel  the  necessity  of  any  sys- 
tem or  of  any  scientific  language  differing  from 
the  common  mode  of  expression  of  his  day.  He 
presents  his  information  as  a  man  with  his  eyes 
open  narrates  in  a  familiar  style  what  he  sees. 
As  civilization  spread  and  science  had  its  repre- 
sentatives in  other  countries  besides  Greece,  it 
became  indispensable  to  have  a  common  scien- 
tific language,  a  technical  nomenclature,  combin- 
ing many  objects  under  common  names,  and 
enabling  every  naturalist  to  express  the  results 
of  his  observations  readily  and  simply  in  a  man- 


16  NOMENCLATURE 

ner  intelligible  to  all  other  students  of  Natural 
History. 

Linnaeus  devised  such  a  system,  and  to  him 
we  owe  a  most  simple  and  comprehensive  scien- 
tific mode  of  designating  animals  and  plants. 
It  may  at  first  seem  no  advantage  to  give  up  the 
common  names  of  the  vernacular  and  adopt  the 
unfamiliar  ones,  but  a  word  of  explanation  will 
make  the  object  clear.  Perceiving,  for  instance, 
the  close  relations  between  certain  members  of 
the  larger  groups,  Linnaeus  gave  to  them  names 
that  should  be  common  to  all,  and  which  are 
called  generic  names,  —  as  we  speak  of  Ducks, 
when  we  would  designate  in  one  word  the  Mal- 
lard, the  Widgeon,  the  Canvas-Back,  etc. ;  but  to 
these  generic  names  he  added  qualifying  epithets, 
called  specific  names,  to  indicate  the  different 
kinds  in  each  group.  For  example,  the  Lion, 
the  Tiger,  the  Panther,  the  Domestic  Cat  consti- 
tute such  a  natural  group,  which  Linnaeus  called 
Felis,  Cat,  indicating  the  whole  genus  ;  but  the 
species  he  designates  as  Felis  catus,  the  Domestic 
Cat,  —  Felis  leo,  the  Lion,  —  Felis  tigris,  the 
Tiger,  —  Felis  panthera,  the  Panther.  So  he 
called  all  the  Dogs  Canis ;  but  for  the  different 
kinds  we  have  Canis  familiaris,  the  Domestic 
Dog,  —  Canis  lupus,  the  Wolf,  —  Canis  vulpes, 
the  Fox,  etc. 

In  some  families  of  the  vegetable  kingdom  we 


AND   CLASSIFICATION.  17 

can  appreciate  better  the  application  of  this  no- 
menclature, because  we  have  something  corre- 
sponding to  it  in  the  vernacular.  We  have,  for 
instance,  one  name  for  all  the  Oaks,  but  we  call 
the  different  kinds  Swamp  Oak,  Red  Oak,  White 
Oak,  Chestnut  Oak,  etc.  So  Linnaeus,  in  his 
botanical  nomenclature,  called  all  the  Oaks  by 
the  generic  name  Quercus,  (characterizing  them 
by  their  fruit,  the  acorn,  common  to  all,)  and 
qualified  them  as  Quercus  bicolor,  Quercus 
rubra,  Quercus  alba,  Quercus  castanea,  etc., 
etc.  His  nomenclature,  being  so  easy  of  ap- 
plication, became  at  once  exceedingly  popular, 
and  made  him  the  great  scientific  legislator  of 
his  century.  He  insisted  on  Latin  names,  be- 
cause, if  every  naturalist  should  use  his  own 
language,  it  must  lead  to  great  confusion,  and 
this  Latin  nomenclature  of  double  significance 
was  adopted  by  all.  Another  advantage  of  this 
binominal  Latin  nomenclature  consists  in  pre- 
venting the  confusion  frequently  arising  from 
the  use  of  the  same  name  to  designate  different 
animals  in  different  parts  of  the  world,  —  as,  for 
instance,  the  name  of  Robin,  used  in  America  to 
designate  a  bird  of  the  Thrush  family,  which  is  en- 
tirely different  from  the  Robin  of  the  Old  World, 
one  of  the  warblers,  —  or  of  different  names  for 
the  same  animal,  as  Perch  or  Chogset  or  Burgall 
for  our  Gunner.  Nothing  is  more  to  be  depre- 


18  NOMENCLATURE 

cated  than  an  over-appreciation  of  technicalities, 
valuing  the  name  more  highly  than  the  thing; 
but  some  knowledge  of  this  scientific  nomencla- 
ture is  necessary  to  every  student  of  Nature. 

While  Linnaeus  pointed  out  classes,  orders, 
genera,  and  species,  other  naturalists  had  de- 
tected other  divisions  among  animals,  called  fam- 
ilies. Lamarck,  who  had  been  a  distinguished 
botanist  before  he  began  his  study  of  the  an- 
imal kingdom,  brought  to  his  zoological  re- 
searches his  previous  methods  of  investigation. 
Families  in  the  vegetable  kingdom  had  long 
been  distinguished  by  French  botanists  ;  and 
one  cannot  examine  the  groups  they  call  by 
this  name,  without  perceiving,  that,  though  they 
bring  them  together  and  describe  them  accord- 
ing to  other  characters,  they  have  been  un- 
consciously led  to  unite  them  from  the  general 
similarity  of  their  port  and  bearing.  Take,  for 
instance,  the  families  of  Pines,  Oaks,  Beeches, 
Maples,  etc.,  and  you  feel  at  once,  that,  besides 
the  common  characters  given  in  the  technical 
descriptions  of  these  different  groups  of  trees, 
there  is  also  a  general  resemblance  among  them 
that  would  naturally  lead  us  to  associate  them 
together,  even  if  we  knew  nothing  of  the  special 
features  of  their  structure.  By  an  instinctive 
recognition  of  this  family  likeness  between 
plants,  botanists  have  been  led  to  seek  for 


AND   CLASSIFICATION.  19 

structural  characters  on  which  to  unite  them, 
and  the  groups  so  founded  generally  correspond 
with  the  combinations  suggested  by  their  ap- 
pearance. 

By  a  like  process  Lamarck  combined  animals 
into  families.  His  method  was  adopted  by 
French  naturalists  generally,  and  found  favor 
especially  with  Cuvier,  who  was  particularly 
successful  in  limiting  families  among  animals, 
and  in  naming  them  happily,  generally  selecting 
names  expressive  of  the  features  on  which  the 
groups  were  founded,  or  borrowing  them  from 
familiar  animals.  Much,  indeed,  depends  upon 
the  pleasant  sound  and  the  significance  of  a 
name  ;  for  an  idea  reaches  the  mind  more  easily 
when  well  expressed,  and  Cuvier's  names  were 
both  simple  and  significant.  His  descriptions 
are  also  remarkable  for  their  graphic  precision, 
—  giving  all  that  is  essential,  omitting  all  that 
is  merely  accessory.  He  has  given  us  the  key- 
note to  his  progress  in  his  own  expressive  lan- 
guage :  — 

"  Je  dus  done,  et  cette  obligation  me  prit  un 
temps  considerable,  je  dus  faire  marcher  de  front 
1'anatomie  et  la  zoologie,  les  dissections  et  le 
classement ;  chercher  dans  mes  premieres  re- 
marques  sur  1' organisation  des  distributions 
meilleures ;  m'en  servir  pour  arriver  a  des  re- 
marques  nouvelles  ;  employer  encore  ces  re- 


20  NOMENCLATURE 

marques  &  perfectionner  les  distributions ;  faire 
sortir  enfin  de  cette  fe*condation  mutuelle  des 
deux  sciences,  1'une  par  1'autre,  un  syst£me 
zoologique  propre  a  servir  d'introducteur  et  de 
guide  dans  le  champ  de  I'auatomie,  et  un  corps 
de  doctrine  anatomique  propre  &  servir  de  de- 
veloppement  et  d'explication  au  syst£me  zoolo- 
gique." * 

It  is  deeply  to  be  lamented  that  so  many  nat- 
uralists have  entirely  overlooked  this  significant 
advice  of  Cuvier's,  with  respect  to  combining 
zoological  and  anatomical  studies  in  order  to 
arrive  at  a  clearer  perception  of  the  true  affini- 
ties among  animals.  To  sum  it  up  in  one  word, 
he  tells  us  that  the  secret  of  his  method  is 
"  comparison,"  —  ever  comparing  and  compar- 
ing throughout  the  enormous  range  of  his 
knowledge  of  the  organization  of  animals,  and 
founding  upon  the  differences  as  well  as  the 
similarities  those  broad  generalizations  under 

*  "  I  therefore  felt  myself  obliged,  and  this  obligation  cost  me 
no  little  time,  to  make  my  studies  in  anatomy  and  zoology,  dissec- 
tion and  classification,  keep  pace  with  each  other ;  to  seek  in  my 
earlier  investigations  upon  organization  a  better  distribution  of 
groups ;  to  employ  these  again  as  a  means  of  perfecting  my 
classification ;  to  arrive,  in  short,  by  this  mutual  fecundation  of 
the  two  sciences  at  a  zoological  system  which  might  serve  as  a 
pioneer  and  guide  in  the  field  of  anatomy,  and  an  anatomical 
method  which  would  aid  in  the  development  and  explanation  of 
the  zoological  system." 


AND   CLASSIFICATION.  21 

which  he  has  included  all  animal  structures. 
And  this  method,  so  prolific  in  his  hands,  has 
also  a  lesson  for  us  all.  In  this  country  there 
is  a  growing  interest  in  the  study  of  Nature ; 
but  while  there  exist  hundreds  of  elementary 
works  illustrating  the  native  aijimals  of  Europe, 
there  are  few  such  books  here  to  satisfy  the  de- 
mand for  information  respecting  the  animals  of 
our  land  and  water.  We  are  thus  forced  to 
turn  more  and  more  to  our  own  investigations 
and  less  to  authority ;  and  the  true  method  of 
obtaining  independent  knowledge  is  this  very 
method  of  Cuvier's,  —  comparison. 

Let  us  make  the  most  common  application  of 
it  to  natural  objects.  Suppose  we  see  together 
a  Dog,  a  Cat,  a  Bear,  a  Horse,  a  Cow,  and  a 
Deer.  The  first  feature  that  strikes  us  as  com- 
mon to  any  two  of  them  is  the  horn  in  the  Cow 
and  Deer.  But  how  shall  we  associate  either  of 
the  others  with  these  ?  We  examine  the  teeth, 
and  find  those  of  the  Dog,  the  Cat,  and  the  Bear 
sharp  and  cutting,  while  those  of  the  Cow,  the 
Deer,  and  the  Horse  have  flat  surfaces,  adapted 
to  grinding  and  chewing,  rather  than  cutting 
and  tearing.  We  compare  these  features  of 
their  structure  with  the  habits  of  these  animals, 
and  find  that  the  first  are  carnivorous,  that  they 
seize  and  tear  their  prey,  while  the  others  are 
herbivorous  or  grazing  animals,  living  only  on 


22  NOMENCLATIVE 

vegetable  substances,  which  they  chew  and 
grind.  We  compare  further  the  Horse  and 
Cow,  and  find  that  the  Horse  has  front  teeth 
both  in  the  upper  and  lower  jaw,  while  the  Cow 
has  them  only  in  the  lower;  and  going  still 
further,  and  comparing  the  internal  with  the  ex- 
ternal features,  we  find  this  arrangement  of  the 
teeth  in  direct  relation  to  the  different  structure 
of  the  stomach  in  the  two  animals,  —  the  Cow 
having  a  stomach  with  four  pouches,  adapted  to 
a  mode  of  digestion  by  which  the  food  is  pre- 
pared for  the  second  mastication,  while  the 
Horse  has  a  simple  stomach.  Comparing  the 
Cow  and  the  Deer,  we  find  that  the  digestive 
apparatus  is  the  same  in  both  ;  but  though  they 
both  have  horns,  in  the  Cow  the  horn  is  hollow, 
and  remains  through  life  firmly  attached  to  the 
bone,  while  in  the  Deer  it  is  solid  and  is  shed 
every  year.  With  these  facts  before  us,  we  can- 
not hesitate  to  place  the  Dog,  the  Cat,  and  the 
Bear  in  one  division,  as  carnivorous  animals, 
and  the  other  three  in  another  division  as  her- 
bivorous animals,  —  and  looking  a  little  further, 
we  perceive,  that,  in  common  with  the  Cow  and 
the  Deer,  the  Goat  and  the  Sheep  have  cloven 
feet,  and  that  they  are  all  ruminants,  while  the 
Horse  has  a  single  hoof,  does  not  ruminate,  and 
must  therefore  be  separated  from  them,  even 
though,  like  them,  he  is  herbivorous. 


AND   CLASSIFICATION.  23 

This  is  but  the  simplest  illustration,  taken 
from  the  most  familiar  objects,  of  this  compar- 
ative method  ;  but  the  same  process  is  equally 
applicable  to  the  most  intricate  problems  in  an- 
imal structures,  and  will  give  us  the  clew  to  all 
true  affinities  between  animals.  The  education 
of  a  naturalist  now  consists  chiefly  in  learning 
how  to  compare.  If  he  have  any  power  of 
generalization,  when  he  has  collected  his  facts, 
this  habit  of  mental  comparison  will  lead  him 
up  to  principles,  and  to  the  great  laws  of  combi- 
nation. It  must  not  discourage  us,  that  the  pro- 
cess is  a  slow  and  laborious  one,  and  the  results 
of  one  lifetime  after  all  very  small.  It  might 
seem  invidious,  were  I  to  show  here  how  small 
is  the  sum  total  of  the  work  accomplished  even 
by  the  great  exceptional  men,  whose  names  are 
known  throughout  the  civilized  world.  But  I 
may  at  least  be  permitted  to  speak  disparagingly 
of  my  own  efforts,  and  to  sum  up  in  the  fewest 
words  the  result  of  my  life's  work.  I  have  de- 
voted my  whole  life  to  the  study  of  Nature,  and 
yet  a  single  sentence  may  express  all  that  I  have 
done.  I  have  shown  that  there  is  a  correspond- 
ence between  the  succession  of  Fishes  in  geologi- 
cal times  and  the  different  stages  of  their  growth 
in  the  egg,  —  this  is  all.  It  chanced  to  be  a 
result  that  was  found  to  apply  to  other  groups 
and  has  led  to  other  conclusions  of  a  like  nature. 


24  NOMENCLATURE 

But,  such  as  it  is,  it  has  been  reached  by  this 
system  of  comparison,  which,  though  I  speak 
of  it  now  in  its  application  to  the  study  of  Nat- 
ural History,  is  equally  important  in  every  other 
branch  of  knowledge.  By  the  same  process  the 
most  mature  results  of  scientific  research  in 
Philology,  in  Ethnology,  and  in  Physical  Sci- 
ence are  reached.  And  let  me  say  that  the 
community  should  foster  the  purely  intellect- 
ual efforts  of  scientific  men  as  carefully  as 
they  do  their  elementary  schools  and  their 
practical  institutions,  generally  considered  so 
much  more  useful  and  important  to  the  public. 
For  from  what  other  source  shall  we  derive  the 
higher  results  that  are  gradually  woven  into  the 
,  practical  resources  of  our  life,  except  from  the 
researches  of  those  very  men  who  study  science, 
not  for  its  uses,  but  for  its  truth  ?  It  is  this  that 
gives  it  its  noblest  interest :  it  must  be  for  truth's 
sake,  and  not  even  for  the  sake  of  its  usefulness 
to  humanity,  that  the  scientific  man  studies  Na- 
ture. The  application  of  science  to  the  useful 
arts  requires  other  abilities,  other  qualities,  other 
tools  than  his  ;  and  therefore  I  say  that  the  man 
of  science  who  follows  his  studies  into  their 
practical  application  is  false  to  his  calling.  The 
practical  man  stands  ever  ready  to  take  up  the 
work  where  the  scientific  man  leaves  it,  and  to 
adapt  it  to  the  material  wants  and  uses  of  daily 
life. 


AND   CLASSIFICATION.  25 

The  publication  of  Cuvier's  proposition,  that 
the  animal  kingdom  is  built  on  four  plans,  how- 
ever imperfectly  understood  and  appreciated  at 
first,  created,  nevertheless,  an  extraordinary  ex- 
citement throughout  the  scientific  world.  All 
naturalists  proceeded  to  test  it,  and  some  among 
them  soon  recognized  in  it  a  great  scientific 
truth,  —  while  others,  who  thought  more  of 
making  themselves  prominent  than  of  advan- 
cing science,  proposed  poor  amendments,  that 
were  sure  to  be  rejected  on  further  investiga 
tion.  Some  of  these  criticisms  and  additions, 
however,  were  truly  improvements,  and  touched 
upon  points  overlooked  by  Cuvier.  Blainville, 
especially,  took  up  the  element  of  form  among 
animals,  —  whether  divided  on  two  sides,  wheth- 
er radiated,  whether  irregular,  etc.  He,  how- 
ever, made  the  mistake  of  giving  very  elaborate 
names  to  animals  already  known  under  simpler 
ones.  Why,  for  instance,  call  all  animals  with 
parts  radiating  in  every  direction  Actinomorpha 
or  Actinozoaria,  when  they  had  received  the 
significant  name  of  Radiates?  It  seemed  to 
be  a  new  system,  when  in  fact  it  was  only  a  new 
name.  Ehrenberg,  likewise,  made  an  important 
distinction,  when  he  united  the  animals  accord- 
ing to  the  difference  in  their  nervous  systems  ; 
but  he  also  encumbered  the  nomenclature  un- 
necessarily, when  he  added  to  the  names  Anaima 


26  NOMENCLATURE 

and  Enaima  of  Aristotle  those  of  Myeloneura 
and  Gang-lioneura. 

But  it  is  not  my  object  to  give  all  the  classifica- 
tions of  different  authors  here,  and  I  will  there- 
fore pass  over  many  noted  ones,  as  those  of  Bur- 
meister,  Milne-Edwards,  Siebold  and  Stannius, 
Owen,  Leuckart,  Vogt,  Van  Beneden,  and  others, 
and  proceed  to  give  some  account  of  one  investi- 
gator who  did  as  much  for  the  progress  of  Zoology 
as  Cuvier,  though  he  is  comparatively  little  known 
among  us. 

Karl  Ernst  von  Baer  proposed  a  classification 
based,  like  Cuvier's,  upon  plan ;  but  he  recognized 
what  Cuvier  failed  to  perceive,  —  namely,  the 
importance  of  distinguishing  between  type  (by 
which  he  means  exactly  what  Cuvier  means  by 
plan)  and  complication  of  structure,  —  in  other 
words,  between  plan  and  the  execution  of  the 
plan.  He  recognized  four  types,  which  corre- 
spond exactly  to  Cuvier's  four  plans,  though  he 
calls  them  by  different  names.  Let  us  compare 
them. 

Cuvier.  Baer. 

Radiates,  Peripherie, 

Mollusks,  Massive, 

Articulates,  Longitudinal, 

Vertebrates.  Doubly  Symmetrical. 

Though  perhaps  less  felicitous,  the  names  of  Baer 
express  the  same  ideas  as  those  of  Cuvier.  By 
the  Peripherie  type  he  signified  those  animals  in 


AND   CLASSIFICATION.  27 

which  all  the  parts  converge  from  the  periphery 
or  circumference  of  the  animal  to  its  centre. 
Cuvier  only  reverses  this  definition  in  his  name 
of  Radiates,  signifying  the  animals  in  which  all 
parts  radiate  from  the  centre  to  the  circumfer- 
ence. By  Massive,  Baer  indicated  those  animals 
in  which  the  body  is  undivided,  soft  and  concen- 
trated, without  a  very  distinct  individualization 
of  parts,  —  exactly  the  animals  included  by  Cu- 
vier under  his  name  of  Mollusks,  or  soft-bodied 
animals.  In  his  selection  of  the  epithet  Longitu- 
dinal, Baer  was  less  fortunate ;  for  all  animals 
have  a  longitudinal  diameter,  and  this  word  was 
not,  therefore,  sufficiently  special.  Yet  his  Lon- 
gitudinal type  answers  exactly  to  Cuvier' s  Articu- 
lates, —  animals  in  which  all  parts  are  arranged 
in  a  succession  of  articulated  joints  along  a  lon- 
gitudinal axis.  Cuvier  has  expressed  this  jointed 
structure  in  the  name  Articulates  ;  whereas  Baer, 
in  his  name  of  Longitudinal,  referred  only  to  the 
arrangement  of  joints  in  longitudinal  succession, 
in  a  continuous  string,  as  it  were,  one  after  an- 
other, indicating  thus  the  prevalence  of  length  as 
the  predominant  diameter  of  the  body.  For  the 
Doubly  Symmetrical  type  his  name  is  the  better 
of  the  two ;  since  Cuvier's  name  of  Vertebrates 
alludes  only  to  the  backbone,  —  while  Baer,  who 
is  an  embryologist,  signifies  in  his  their  mode  of 
growth  also.  He  knew  what  Cuvier  did  not 


28  NOMENCLATURE 

know,  when  he  first  proposed  his  classification, 
that  in  its  first  formation  the  gerni  of  the  Verte- 
brate divides  in  two  folds  ;  one  turning  up  above 
the  backbone,  to  form  and  enclose  all  the  sensitive 
organs,  —  the  spinal  marrow,  the  organs  of  sense, 
all  those  organs  by  which  life  is  expressed ;  the 
other  turning  down  below  the  backbone,  and  en- 
closing all  those  organs  by  which  life  is  main- 
tained, —  the  organs  of  digestion,  of  respiration, 
of  circulation,  of  reproduction,  etc.  So  there  is  in 
this  type  not  only  an  equal  division  of  parts  on 
either  side,  but  also  a  division  above  and  below, 
making  thus  a  double  symmetry  in  the  plan,  ex- 
pressed by  Baer  in  the  name  he  gave  it.  Baer 
was  perfectly  original  in  his  conception  of  these 
four  types,  for  his  paper  was  published  in  the  very 
same  year  with  that  of  Cuvier.  But  even  in  Ger- 
many, his  native  land,  his  ideas  were  not  fully 
appreciated:  strange  that  it  should  be  so,  —  for, 
had  his  countrymen  recognized  his  genius,  they 
might  have  earlier  claimed  him  as  the  compeer 
of  the  great  French  naturalist. 

Baer  also  founded  the  science  of  Embryology, 
under  the  guidance  of  his  teacher,  Dollinger. 
His  researches  in  this  direction  showed  him  that 
animals  were  not  only  built  on  four  plans,  but 
that  they  grew  according  to  four  modes  of  devel- 
opment. The  Vertebrate  arises  from  the  egg 
differently  from  the  Articulate,  —  the  Articulate 


AND   CLASSIFICATION.  29 

differently  from  the  Mollusk,  —  the  Mollusk  dif- 
ferently from  the  Radiate.  Cuvier  only  showed 
us  the  four  plans  as  they  exist  in  the  adult ;  Baer 
went  a  step  further,  and  showed  us  the  four  plans 
in  the  process  of  formation. 

But  his  greatest  scientific  achievement  is  per- 
haps the  discovery  that  all  animals  originate  from 
eggs,  and  that  all  these  eggs  are  at  first  identical 
in  substance  and  structure.  The  wonderful  and 
untiring  research  condensed  into  this  simple 
statement,  that  all  animals  arise  from  eggs,  and 
that  all  those  eggs  are  identical  in  the  beginning, 
may  well  excite  our  admiration.  This  egg  con- 
sists of  an  outer  envelope,  the  vitelline  membrane, 
containing  a  fluid  more  or  less  dense,  and  various- 
ly colored,  the  yolk  ;  within  this  is  a  second  en- 
velope, the  so-called  germinative  vesicle,  contain- 
ing a  somewhat  different  and  more  transparent 
fluid,  and  in  the  fluid  of  this  second  envelope 
float  one  or  more  so-called  germinative  specks. 
At  this  stage  of  their  growth  all  eggs  are  micro- 
scopically small,  yet  each  one  has  such  tenacity 
of  its  individual  principle  of  life  that  no  egg  was 
ever  known  to  swerve  from  the  pattern  of  the 
parent  animal  that  gave  it  birth. 


30  CATEGORIES   OF   CLASSIFICATION. 


CHAPTER  III. 

CATEGORIES  OF  CLASSIFICATION. 

FROM  the  time  that  Linnaeus  showed  us  the 
necessity  of  a  scientific  system  as  a  framework  for 
the  arrangement  of  scientific  facts  in  Natural 
History,  the  number  of  divisions  adopted  by  zo- 
ologists and  botanists  increased  steadily.  Not 
only  were  families,  orders,  and  classes  added  to 
genera  and  species,  but  these  were  further  multi- 
plied by  subdivisions  of  the  different  groups.  But 
as  the  number  of  divisions  increased,  they  lost  in 
precise  meaning,  and  it  became  more  and  more 
doubtful  how  far  they  were  true  to  Nature. 
Moreover,  these  divisions  were  not  taken  in  the 
same  sense  by  all  naturalists :  what  were  called 
families  by  some  were  called  orders  by  others, 
while  the  orders  of  some  were  the  classes  of  oth- 
ers, till  it  began  to  be  doubted  whether  these 
scientific  systems  had  any  foundation  in  Nature, 
or  signified  anything  more  than  that  it  had 
pleased  Linnaeus,  for  instance,  to  call  certain 
groups  of  animals  by  one  name,  while  Cuvier 
had  chosen  to  call  them  by  another. 


CATEGORIES   OF   CLASSIFICATION.  31 

These  divisions  are,  first,  the  most  comprehen- 
sive groups,  the  primary  divisions,  called  branches 
by  some,  types  by  others,  and  divided  by  some 
naturalists  into  so-called  sub-types,  meaning  only 
a  more  limited  circumscription  of  the  same  kind 
of  group  ;  next  we  have  classes,  and  these  also 
have  been  divided  into  sub-classes;  then  orders 
and  sub-orders ;  families  and  sub-families  or 
tribes ;  then  genera,  species,  and  varieties.  With 
reference  to  the  question  whether  these  groups 
really  exist  in  Nature,  or  are  merely  the  expres- 
sion of  individual  theories  and  opinions,  it  is 
worth  while  to  study  the  works  of  the  early  natu- 
ralists, in  order  to  trace  the  natural  process  by 
which  scientific  classification  has  been  reached ; 
for  in  this,  as  in  other  departments  of  learning, 
practice  has  always  preceded  theory.  We  do  the 
thing  before  we  understand  why  we  do  it :  speech 
precedes  grammar,  reason  precedes  logic ;  and  so 
a  division  of  animals  into  groups,  upon  an  in- 
stinctive perception  -of  their  differences,  has  pre- 
ceded all  our  scientific  creeds  and  doctrines.  Let 
us,  therefore,  proceed  to  examine  the  meaning 
of  these  names  as  adopted  by  naturalists. 

When  Cuvier  proposed  his  four  primary  di- 
visions of  the  animal  kingdom,  he  added  his 
argument  for  their  adoption,  —  because,  he  said, 
they  are  constructed  on  four  different  plans. 
All  the  progress  in  our  science  since  his  time 


32  CATEGOEIES   OF   CLASSIFICATION. 

confirms  this  result ;  and  I  shall  attempt  to 
show  that  there  are  really  four,  and  only  four, 
such  structional  ideas  at  the  foundation  of  the 
animal  kingdom,  and  that  all  animals  are  in- 
cluded under  one  or  another  of  them.  But  it 
does  not  follow,  that,  because  we  have  arrived 
at  a  sound  principle,  we  are  therefore  unerring 
in  our  practice.  From  ignorance  we  may  mis- 
place animals,  and  include  them  under  the 
wrong  division.  This  is  a  mistake,  however, 
which  a  better  insight  into  their  organization 
rectifies  ;  and  experience  constantly  proves,  that, 
whenever  the  structure  of  an  animal  is  perfectly 
understood,  there  is  no  hesitation  as  to  the  head 
under  which  it  belongs.  We  may  consequently 
test  the  merits  of  these  four  primary  groups  on 
the  evidence  furnished  by  investigation. 

It  has  already  been  seen  that  these  plans  may 
be  presented  in  the  most  abstract  manner  with- 
out any  reference  to  special  animals.  Radiation 
expresses  in  one  word  the  idea  on  which  the 
lowest  of  these  types  is  based.  In  Radiates  we 
have  no  prominent  bilateral  symmetry,  such  as 
exists  in  all  other  animals,  but  an  all-sided 
symmetry,  in  which  there  is  no  right  and  left, 
no  anterior  and  posterior  extremity,  no  above 
and  below.  It  is  true  that  in  some  of  them 
there  are  indications  of  that  bilateral  symmetry 
which  becomes  a  law  in  the  higher  animals ;  but 


CATEGORIES   OF  CLASSIFICATION.  33 

wherever  such  a  tendency  is  perceptible  in  the 
Radiates  it  is  subordinate  to  the  typical  plan  on 
which  the  whole  group  is  founded.  They  are 
spheroidal  bodies  ;  yet,  though  many  of  them 
remind  us  of  a  sphere,  they  are  by  no  means 
to  be  compared  to  a  mathematical  sphere,  but 
rather  to  an  organic  sphere,  so  loaded  with  life, 
as  it  were,  as  to  produce  an  infinite  variety  of 
radiate  symmetry.  The  mathematical  sphere 
has  a  centre  to  which  every  point  of  the  sur- 
face bears  identical  relations  ;  such  spheres  do 
not  exist  in  the  Animal  Kingdom.  A  sphere 
of  revolution,  in  consequence  of  its  rotation  up- 
on its  axis,  presents  equally  flattened  poles  with 
meridians  of  equal  value  ;  this  also  is  no  organic 
character.  A  living  sphere  has  unequal  poles 
as  well  as  unequal  meridians,  however  much  it 
may  resemble  a  perfectly  spheroidal  body,  and 
the  whole  organization  is  arranged,  not  neces- 
sarily around  a  centre,  but  always  around  a 
vertical  axis,  to  which  the  parts  bear  equal  re- 
lations. 

In  Mollusks  there  is  a  longitudinal '  axis  and 
a  bilateral  symmetry  ;  but  the  longitudinal 
axis  in  these  soft  concentrated  bodies  is  not 
very  prominent,  except  in  the  highest  class ; 
and  though  the  two  ends  of  this  axis  are  dis- 
tinct from  each  other,  the  difference  is  not  so 
marked  that  we  can  say  at  once,  for  all  of 

2*  C 


34  CATEGORIES   OF   CLASSIFICATION. 

them,  which  is  the  anterior  and  which  the  pos- 
terior extremity.  In  this  type,  right  and  left 
have  the  preponderance  over  the  other  diame- 
ters of  the  body.  The  sides  are  the  prominent 
parts,  —  they  are  loaded  with  the  most  impor- 
tant organs,  or  with  those  peculiarities  of  the 
structure  that  give  it  character.  The  Oyster 
is  a  good  instance  of  this,  with  its  double  valve, 
so  swollen  on  one  side,  so  flat  on  the  other. 
There  is  an  unconscious  recognition  of  this  in 
the  arrangement  of  all  collections  of  Mollusks ; 
for,  though  the  collectors  do  not  put  up  their 
specimens  with  any  intention  of  illustrating  this 
peculiarity,  they  instinctively  give  them  the  po- 
sition best  calculated  to  display  their  distinctive 
characteristics,  and  to  accomplish  this  they  ne- 
cessarily place  them  in  such  a  manner  as  to 
show  the  sides. 

In  Articulates  there  is  also  a  longitudinal  axis 
of  the  body  and  a  bilateral  symmetry  in  the 
arrangement  of  parts  ;  the  head  and  tail  are 
marked,  and  the  right  and  left  sides  are  dis- 
tinct. But  the  prominent  tendency  in  this  type 
is  the  development  of  the  dorsal  and  ventral 
region ;  here  above  and  below  prevail  over  right 
and  left.  It  is  the  back  and  the  lower  side  that 
have  the  preponderance  over  any  other  part  of 
the  structure  in  Articulates.  The  body  is  divided 
from  end  to  end  by  a  succession  of  transverse 


CATEGORIES    OF    CLASSIFICATION.  35 

constrictions,  forming  movable  rings ;  but  the 
striking  features  of  the  animal  are  always  above 
or  below,  and  especially  developed  on  the  back. 
Any  collection  of  Insects  or  Crustacea  is  an 
evidence  of  this  ;  being  always  instinctively  ar- 
ranged in  such  a  manner  as  to  show  the  pre- 
dominant features,  they  uniformly  exhibit  the 
back  of  the  animal.  The  profile  view  of  an 
Articulate  has  no  significance ;  whereas  in  a 
Mollusk,  on  the  contrary,  the  profile  view  is 
the  most  illustrative  of  the.  structural  char- 
acter. 

In  the  highest  division,  the  Vertebrates,  so 
characteristically  called  by  Baer  the  Doubly 
Symmetrical  type,  a  solid  column  runs  through 
the  body  with  an  arch  above  and  an  arch  below, 
thus  forming  a  double  internal  cavity.  In  this 
type,  the  head  is  the  prominent  feature ;  it  is, 
as  it  were,  the  loaded  end  of  the  longitudinal 
axis,  so  charged  with  vitality  as  to  form  an  in- 
telligent brain,  and  rising  in  man  to  such  pre- 
dominance as  to  command  and  control  the  whole 
organism.  The  structure  is  arranged  above  and 
below  this  axis,  the  upper  cavity  containing,  as 
we  have  seen  above,  all  the  sensitive  organs, 
and  the  lower  cavity  containing  all  those  by 
which  life  is  maintained. 

While  Cuvier  and  his  followers  traced  these 
four  distinct  plans,  as  shown  in  the  adult  ani- 


36  CATEGORIES   OF   CLASSIFICATION. 

mal,  Baer  opened  to  us  a  new  field  of  investi- 
gation in  the  embryology  of  the  four  types, 
showing  that  for  each  there  was  a  special  mode 
of  growth  in  the  egg.  Looking  at  them  from 
this  point  of  view,  we  shall  see  that  these  four 
types,  with  their  four  modes  of  growth,  seem  to 
fill  out  completely  the  plan  or  outline  of  the 
animal  kingdom,  and  leave  no  reason  to  expect 
any  further  development  or  any  other  plan  of 
animal  life  within  these  limits.  The  eggs  of  all 
animals  are  spheres,  such  as  I  have  described 
them;  but  in  the  Radiate  the  whole  periphery  is 
transformed  into  the  germ,  so  that  it  becomes, 
by  the  liquefying  of  the  yolk,  a  hollow  sphere. 
In  the  Mollusks,  the  germ  lies  above  the  yolk, 
absorbing  its  whole  substance  through  the  under 
side,  thus  forming  a  massive  close  body  instead 
of  a  hollow  one.  In  the  Articulate,  the  germ 
is  turned  in  a  position  exactly  opposite  to  that 
of  the  Mollusk,  and  absorbs  the  yolk  upoji  the 
back.  In  the  Vertebrate,  the  germ  divides  in 
two  folds,  one  turning  upward,  the  other  turning 
downward,  above  and  below  the  central  backbone. 
These  four  modes  of  development  seem  to  ex- 
haust the  possibilities  of  the  primitive  sphere, 
which  is  the  foundation  of  all  animal  life,  and 
therefore  I  believe  that  Cuvier  and  Baer  were 
right  in  saying  that  the  whole  animal  kingdom 
is  included  under  these  four  structural  ideas. 


CATEGORIES   OF   CLASSIFICATION.  37 

Leuckart  proposed  to  subdivide  the  Radiates  in- 
to two  groups :  the  Coelenterata,  including  Polyps 
and  Acalephs  or  Jelly-Fishes,  —  and  Echino- 
derms,  including  Star-Fishes,  Sea-Urchins,  and 
Holothurians.  His  reason  for  this  distinction 
is  the  fact,  that  in  the  latter  the  organs  or 
cavities  of  the  body  have  walls  of  their  own, 
distinct  from  the  body-wall;  whereas  in  the 
former  they  are  formed  by  internal  folds  of  the 
outer  wall  of  the  body,  as  in  the  Polyps,  or  are 
hollowed  out  of  the  substance  of  the  body,  as 
in  Jelly-Fishes.  This  implies  no  difference  in 
the  plan,  but  merely  a  difference  in  the  execu- 
tion of  the  plan.  Both  are  equally  radiate  in 
their  structure  ;  and  when  Leuckart  separated 
them  as  distinct  primary  types,  he  mistook  a 
difference  in  the  material  expression  of  the 
plan  for  a  difference  in  the  plan  itself. 

So  some  naturalists  have  distinguished  Worms 
from  the  other  Articulates  as  a  separate  prime 
division.  But  the  structural  plan  of  this  type  is 
a  cylinder  divided  by  transverse  constrictions  or 
joints ;  and  whether  those  joints  are  uniformly 
arranged  from  one  end  of  the  body  to  the  other, 
as  in  the  Worms,  or  whether  the  front  joints 
are  soldered  together  so  as  to  form  two  regions 
of  the  body,  as  in  Crustacea,  or  divided  so  as 
to  form  three  regions  of  the  body,  as  in  winged 
insects,  does  not  in  the  least  affect  the  typical 


38  CATEGORIES   OF   CLASSIFICATION. 

character  of  the  structure,  which  remains  the 
same  in  all,  being,  in  fact,  an  articulated  cylin- 
der with  variously  combined  rings  and  more  or 
less  complicated  tubular  appendages. 

Branches  or  types,  then,  are  natural  groups 
of  the  animal  kingdom,  founded  on  plans  of 
structure  or  structural  ideas.  What  now  are 
classes  ?  Are  they  lesser  divisions,  differing  only 
in  extent,  or  are  they  founded  on  special  charac- 
ters ?  I  believe  the  latter  view  to  be  the  true 
one,  and  that  class  characters  have  a  signifi- 
cance quite  different  from  that  of  their  mere 
range  or  extent.  These  divisions  are  founded 
on  certain  categories  of  structure ;  and  were 
there  but  one  animal  of  a  class  in  the  world, 
if  it  had  those  characters  on  which  a  class  is 
founded,  it  would  be  as  distinct  from  all  other 
classes  as  if  its  kind  were  counted  by  thousands. 

Baer  approached  the  idea  of  the  classes  when 
he  discriminated  between  plan  of  structure  or 
type  and  the  degree  of  perfection  in  the  struc- 
ture. But  while  he  understands  the  distinction 
between  a  plan  and  its  execution,  his  ideas  re- 
specting the  different  features  of  structure  are 
not  quite  so  precise.  He  does  not,  for  instance, 
distinguish  between  the  complication  of  a  given 
structure  and  the  mode  of  execution  of  a  plan, 
both  of  which  are  combined  in  what  he  calls 
degrees  of  perfection.  And  yet,  without  this 


CATEGORIES   OF   CLASSIFICATION.  39 

distinction,  the  difference  between  classes  and 
orders  cannot  be  understood;  for  classes  and 
orders  rest  upon  a  just  appreciation  of  these  two 
categories,  which  are  quite  distinct  from  each 
other,  and  have  by  no  means  the  same  signifi- 
cance. 

Again,  quite  distinct  from  both  of  these  is  the 
character  of  form,  not  to  be  confounded  either 
with  complication  of  structure,  on  which  orders 
are  based,  or  with  the  execution  of  the  plan,  on 
which  classes  rest.  An  example  will  show  that 
form  is  no  guide  for  the  determination  of  classes 
or  orders.  Take,  for  instance,  a  Beche-de-Mer, 
a  member  of  the  highest  class  of  Radiates,  and 
compare  it  with  a  Worm.  They  are  both  long 
cylindrical  bodies  ;  but  one  has  parallel  divisions 
along  the  length  of  the  body,  the  other  has  the 
body  divided  by  transverse  rings.  Though  in 
external  form  they  resemble  each  other,  the  one 
is  a  worm-like  Radiate,  the  other  is  a  worm-like 
Articulate,  each  having  the  structure  of  its  own 
type ;  so  that  they  do  not  even  belong  to  the 
same  great  division  of  the  animal  kingdom,  much 
less  to  the  same  class.  We  have  a  similar  in- 
stance in  the  Whales  and  Fishes,  —  the  Whales 
having  been  for  a  long  time  considered  as  Fishes, 
on  account  of  their  form,  while  their  structural 
complication  shows  them  to  be  a  low  order  of  the 
class  of  Mammalia,  to  which  we  ourselves  belong, 


40  CATEGORIES   OF   CLASSIFICATION. 

that  class  being  founded  upon  a  particular  mode 
of  execution  of  the  plan  characteristic  of  the  Ver- 
tebrates, while  the  order  to  which  the  Whales 
belong  depends  upon  their  complication  of  struc- 
ture, as  compared  with  other  members  of  the 
same  class. 

We  may  therefore  say  that  neither  form  nor 
complication  of  structure  distinguishes  classes, 
but  simply  the  mode  of  execution  of  a  plan.  In 
Vertebrates,  for  instance,  how  do  we  distinguish 
the  class  of  Mammalia  from  the  other  classes  of 
the  type  ?  By  the  peculiar  development  of  the 
brain,  by  their  breathing  through  lungs,  by  their 
double  circulation,  by  their  bringing  forth  living 
young  and  nursing  them  with  milk.  In  this 
class  the  beasts  of  prey  form  a  distinct  order, 
superior  to  the  Whales  or  the  herbivorous  ani- 
mals, on  account  of  the  higher  complication  of 
their  structure ;  and  for  the  same  reason  we 
place  the  Monkeys  above  them  all.  But  among 
the  beasts  of  prey  we  distinguish  the  Bears,  as  a 
family,  from  the  family  of  Dogs,  Wolves,  and 
Cats,  on  account  of  their  different  form,  which 
does  not  imply  a  difference  either  in  the  compli- 
cation of  their  structure  or  in  the  mode  of  execu- 
tion of  their  plan. 


CLASSIFICATION  AND   CREATION.  41 


CHAPTER  IV. 

CLASSIFICATION  AND   CREATION. 

So  close  is  the  connection  between  classifica- 
tion and  the  plan  of  creation,  the  former  being,  so 
far  as  it  is  accurate,  the  literal  interpreter  of 
the  latter,  that  the  efforts  of  men  to  detect  the 
natural  affinities  among  animals,  and  to  express 
them  in  clear,  condensed  forms,  have  always  been 
recognized  as  the  highest  creations  of  scientific 
genius.  Creations  they  were  not,  since  the  only 
valid  classification  is  already  recorded  in  organic 
forms,  and  a  classification  which  is  true  to  nature 
cannot  be  original ;  but  works  of  genius  some  of 
them  have  unquestionably  been,  embodying  the 
laborious,  life-long  investigations  of  men  whose 
powerful  imaginations  vitalized  anew  the  dead 
facts  they  collected.  Such  are  the  systems  of 
classification  of  Linnaeus,  of  Cuvier,  of  von  Baer. 
And  while  in  presenting  classification  as  the 
subject  of  a  series  of  papers  in  the  "Atlantic 
Monthly,"  I  am  aware  that  I  am  drawing  largely 
upon  the  patience  of  its  readers,  since  the  tech- 
nical nature  of  the  topic  renders  many  details 


42  CLASSIFICATION  AND   CREATION. 

necessary  which  cannot  be  otherwise  than  dry  to 
any  but  professional  naturalists ;  yet  believing, 
as  I  do,  that  classification,  rightly  understood, 
means  simply  the  creative  plan  of  God  as  ex- 
pressed in  organic  forms,  I  feel  the  importance 
of  attempting  at  least  to  present  it  in  a  popular 
guise,  divested,  as  far  as  possible,  of  technical- 
ities. I  would  therefore  ask  the  indulgence  of 
my  readers  for  such  scientific  terms  and  details 
as  cannot  well  be  dispensed  with,  begging  them 
to  remember  that  a  long  and  tedious  road  may 
bring  us  suddenly  upon  a  glorious  prospect,  and 
that  a  clearer  mental  atmosphere  and  a  new  in- 
tellectual sensation  may  well  reward  us  for  a 
little  weariness  in  the  outset. 

Besides,  the  time  has  come  when  scientific 
truth  must  cease  to  be  the  property  of  the  few, 
when  it  must  be  woven  into  the  common  life  of 
the  world  ;  for  we  have  reached  the  point  where 
the  results  of  science  tpuch  the  very  problem  of 
existence,  and  all  men  listen  for  the  solving  of 
that  mystery.  When  it  will  come,  and  how, 
none  can  say ;  but  this  much  at  least  is  certain, 
that  all  our  researches  are  leading  up  to  that 
question,  and  mankind  will  never  rest  till  it  is 
answered.  If,  then,  the  results  of  science  are  of 
such  general  interest  for  the  human  race,  if  they 
are  gradually  interpreting  the  purposes  of  the 
Deity  in  creation,  and  the  relation  of  man  to  all 


CLASSIFICATION  AND   CREATION.  43 

the  past,  then  it  is  well  that  all  should  share  in 
its  teachings,  and  that  it  should  not  be  kept,  like 
the  learning  of  the  Egyptians,  for  an  exclusive 
priesthood  who  may  expound  the  oracle  accord- 
ing to  their  own  theories,  but  should  make  a  part 
of  all  our  intellectual  culture  and  of  our  com- 
mon educational  systems.  With  this  view,  I  will 
endeavor  to  simplify  as  far  as  may  be  my  illus- 
trations of  the  different  groups  of  the  Animal 
Kingdom,  beginning  with  a  more  careful  analysis 
of  those  structural  features  on  which  classes  are 
founded. 

I  have  said  that  the  Radiates  are  the  lowest 
type  among  animals,  embodying,  under  an  infinite 
variety  of  forms,  that  plan  in  which  all  parts  bear 
definite  relations  to  a  vertical  central  axis.  The 
three  classes  of  Radiates  are  distinguished  from 
each  other  by  three  distinct  ways  of  executing 
that  plan.  I  dwell  upon  this  point ;  for  we  shall 
never  arrive  at  a  clear  understanding  of  the  dif- 
ferent significance  and  value  of  the  various 
divisions  of  the  Animal  Kingdom,  till  we  appre- 
ciate the  distinction  between  the  structural  con- 
ception and  the  material  means  by  which  it  is 
expressed.  A  comparison  will,  perhaps,  better 
explain  my  meaning.  There  are  certain  archi- 
tectonic types,  including  edifices  of  different 
materials,  with  an  infinite  variety  of  architec- 
tural details  and  external  ornaments;  but  the 


44  CLASSIFICATION  AND   CREATION. 

flat  roof  and  the  colonnade  are  typical  of  all 
Grecian  temples,  whether  built  of  marble  or 
granite  or  wood,  whether  Doric  or  Ionic  or 
Corinthian,  whether  simple  and  massive  or  light 
and  ornamented  ;  and,  in  like  manner,  the  steep 
roof  and  pointed  arch  are  the  typical  characters 
of  all  Gothic  cathedrals,  whatever  be  the  material 
or  the  details.  The  architectural  conception  re- 
mains the  same  in  all  its  essential  elements,  how- 
ever the  more  superficial  features  vary.  Such 
relations  as  these  edifices  bear  to  the  architec- 
tural idea  that  includes  them  all,  do  classes  bear 
to  the  primary  divisions  or  branches  of  the  Ani- 
mal Kingdom. 

The  three  classes  of  Radiates,  beginning  with 
the  lowest,  and  naming  them  in  their  relative 
order,  are  Polyps  or  Sea-anemones  and  corals, 
Acalephs  or  Jelly-Fishes,  and  Echinoderms  or 
Star-Fishes,  Sea-Urchins  and  the  like.  In  the 
Polyps  the  plan  is  executed  in  the  simplest 
manner ;  the  body  consists  of  a  sac,  the  sides 
of  which  are  folded  inward,  at  regular  intervals, 
from  top  to  bottom,  so  as  to  divide  it  by  vertical 
radiating  partitions,  converging  from  the  periph- 
ery toward  the  centre.  These  folds  do  not  meet 
in  the  centre,  but  leave  an  open  space,  which  is 
the  main  cavity  of  the  body.  This  open  space, 
however,  occupies  only  the  lower  part  of  the 
body;  for  in  the  upper  there  is  a  second  sac 


CLASSIFICATION   AND   CREATION. 


45 


hanging  to  a  certain  distance  within  the  first. 
This  inner  sac  has  an  aperture  in  the  bottom, 
through  which  whatever  enters  it  passes  into  the 
main  cavity  of  the  body.  A  central  opening  in 


Vertical  section  of  a  contracted  Sea- Anemone  or  Actinia  :  o,  mouth  5  <,  ten- 
tacles 5  s,  inner  sac  or  stomach  ;  ft,  main  cavity  •,  //,  reproductive  organs  ; 
g,  radiating  partition  ;  eee,  radiating  chambers  ;  c  c,  circular  openings 
in  the  partitions  ;  a  a,  lower  floor.  The  tentacles  are  drawn  in. 

the  top  forms  a  kind  of  mouth,  around  which 
are  radiating  tentacles  connecting  with  the  open 
chambers  formed  by  the  partitions  within.  Cut- 


Sea-Anemone  or  Actinia,  moderately  expanded. 

ting  such  an  animal  across  in  a  transverse  sec- 
tion, we  shall  see  the  radiation  of  the  partitions 


46  CLASSIFICATION   AND    CREATION. 

from  the  centre  to  the  circumference,  showing 


Transverse  section  of  a  Sea- Anemone  or  Actinia. 

still  more  distinctly  the  typical  structure  of  the 
division  to  which  it  belongs. 

The   second   class   is   that   of  Jelly-Fishes  or 
Acalephs ;  and  here  the  same  plan  is  carried  out 


Staurophora  seen  in  profile. 

in  the  form  of  a  hemispherical  gelatinous  disk, 
the   digestive   cavity  being  hollowed,  or,   as   it 


Hippocrene  seen  in  profile. 

were,  scooped,  out  of  the  substance  of  the  body, 
which  is   traversed  by  tubes  that  radiate  from 


CLASSIFICATION  AND   CREATION.  '   47 

the  centre  to  the  periphery.  Cutting  it  across 
transversely,  or  looking  through  its  transparent 
mass,  the  same  radiation  of  the  internal  structure 
is  seen  again ;  only  that  in  this  instance  the  radi- 
ating lines  are  not  produced  by  vertical  partition- 
walls,  with  open  spaces  between,  as  in  the  Polyps, 
but  by  radiating  tubes  passing  through  the  ge- 
latinous mass  of  the  body.  At  the  periphery  is  a 


Melicertum  seen  from  above,  with  the  tentacles  spreading :  o  o,  radiating  tubes 
with  ovaries  ;  TO,  mouth  ;  1 1  tt,  tentacles. 

circular  tube  connecting  them  all,  and  the  tenta- 
cles, which  hang  down  when  the  animal  is  in  its 
natural  position,  connect  at  their  base  with  the 
radiating  tubes,  while  numerous  smaller  -tentacles 
may  form  a  kind  of  fringe  all  round  the  margin. 

The  third  and  highest  class  includes  the  Star- 
Fishes,  Sea-Urchins,  and  Holothurians  or  Beches- 
de-Mer.  The  radiation  is  equally  distinct  in  each 
of  these  ;  but  here  again  the  mode  of  execu- 
tion differs  from  that  of  the  two  other  classes. 


48 


CLASSIFICATION  AND   CREATION. 


The  internal  cavity  and  the  radiating  tubes,  in- 
stead of  being  connected  with  the  outer  wall  of 


Common  Sea-Urchin,  Echinus,  seen  from  above. 

the  body  as  in  Polyps,  or  hollowed  out  of  the 
substance  of  the  body  as  in  Jelly-Fishes,  are  here 
enclosed  within  independent  walls  of  their  own, 


Echinarachnius,  opened  by  a  transverse  or  horizontal  section,  and  showing 
the  internal  arrangement -.  o,  mouth  ;  e  eee  e,  ambulacra,  with  their  rami- 
fications cm  cm  cm;  wwww,  interambulacra. 

quite  distinct  from  the  wall  of  the  body.     But 
notwithstanding  this  difference,  a  transverse  sec- 


CLASSIFICATION  AND   CEEATION.  49 

tion  shows  in  these  animals,  as  distinctly  as  in  all 
the  rest,  the  radiating  structure  typical  of  the 
whole  branch.  In  these  three  classes  we  have 
no  difference  of  plan,  nor  even  any  modification 
of  the  same  plan,  —  for  either  one  of  them  ex- 
presses it  as  clearly  as  any  other,  —  but  simply 
three  different  ways  of  executing  one  and  the 
same  structural  idea. 

To'  those  already  familiar  with  these  animals 
some  technical  details  showing  the  absolute  iden- 
tity of  structural  plan  in  these  three  classes  of 
Radiates  may  not  be  uninteresting. 

Let  us  therefore  return  to  the  Polyps,  and  look 
at  the  Sea-Anemone  in  a  new  aspect.  Sup- 
pose the  inner  sac  to  be  turned  out;  it  will 
then  present  the  appearance  of  a  bottle-shaped 
body,  with  a  row  of  hollow  projections  around 
the  base  of  the  neck ;  the  neck  itself  being  the 
stomach  turned  outward,  so  that  its  inner  surface 
becomes  its  outer  surface.  If  we  now  compare 
this  with  the  Jelly-Fish,  placing  both  in  the  same 
attitude,  with  the  mouth  either  downward  or 
upward,  it  becomes  apparent  that  the^  so-called 
arms  surrounding  the  mouth  of  the  Jelly-Fish 
correspond  exactly  to  the  neck  of  our  bottle- 
shaped  animal,  with  the  sole  difference  that  it 
is  split  into  lobes  in  the  Jelly-Fish,  instead  of 
remaining  tubular  as  in  the  Polyp.  There  are, 
however,  many  Jelly-Fishes  in  which  it  is  strictly 


50  CLASSIFICATION  AND   CREATION. 

tubular  as  in  the  Polyps.  To  carry  the  com- 
parison further,  widen  the  partitions  between  the 
chambers  of  the  Polyps,  and  the  chambers  are  then 
reduced  to  narrow  tubes,  which  completes  the  ho- 
mology.  In  Echinoderms  the  diiference  consists, 
as  we  have  seen,  in  the  fact  that  the  various  cav- 
ities of  the  body,  instead  of  being  simply  scooped 
out  of  its  substance,  have  walls  of  their  own  ; 
these  walled  cavities  being  enclosed  as  intestines 
by  the  outer  wall  of  the  body.  I  shall  return  to 
this  subject  again,  when  I  explain  the  homolo- 
gies  of  Radiates  more  in  detail,  but  have  thought 
it  well  to  allude  to  it  here  in  connection  with 
this  more  general  sketch  of  their  structure. 

I  have  mentioned  only  three  classes  of  Radi- 
ates. Cuvier  had  five  in  his  classification ;  for 
he  had  placed  among  them  the  Intestinal  Worms 
and  the  Infusoria  or  Animalcules.  The  Intes- 
tinal Worms  are  much  better  known  now  than 
they  were  in  his  day.  Their  anatomy  and  em- 
bryology have  been  traced,  and  it  has  been  shown 
that  the  essential  features  of  these  parasites  are 
the  same  as  those  of  all  Articulates,  their  whole 
body  being  divided  into  successive  movable  joints 
or  rings.  Cuvier  was  misled  by  the  circular  ar- 
rangement of  certain  parts  around  the  mouth, 
and  by  the  presence  of  a  wreath  of  feelers  around 
the  head  of  some  of  these  Worms,  resembling  the 
tentacles  of  many  Radiates.  This  is,  however, 


CLASSIFICATION  AND   CREATION.  51 

no  indication  of  radiate  structure,  but  a  super- 
ficial feature  in  no  way  related  to  the  internal 
organization  ;  and  therefore  the  Intestinal  Worms 
must  be  removed  from  the  branch  of  Radiates, 
and  referred  to  that  of  Articulates. 

We  must  carefully  distinguish  between  affinity 
and  analogy  among  animals.  The  former  is 
founded  on  identity  of  plan  ;  the  latter  only  upon 
external  resemblance.  This  may  be  produced  by 
similar  features,  which,  when  intimately  connected 
with  the  whole  internal  organization,  as  in  some 
groups,  may  be  considered  as  typical  characters, 
but  when  only  grafted,  as  it  were,  in  a  superficial 
manner  on  animals  of  another  type,  have  no  re- 
lation to  the  essential  elements  of  structure,  and 
become  at  once  subordinate  and  unimportant. 
Such  is  the  difference  between  the  tentacles  in  a 
Radiate  and  the  wreath  of  feelers  in  a  Worm  ;  — 
the  external  effect  may  be  much  the  same  ;  but 
in  the  former  every  tentacle  opens  into  one  of 
the  chambers,  as  in  a  Polyp,  or  connects  with  one 
of  the  radiating  tubes,  as  in  Acalephs,  or  with  the 
locomotive  suckers,  as  in  Star-Fishes,  and  is  there- 
fore closely  linked  with  the  whole  internal  or- 
ganization ;  whereas  the  feelers  in  the  latter  are 
only  external  appendages,  in  no  way  connected 
with  the  essential  structural  elements.  We  have 
a  striking  illustration  of  this  superficial  resem- 
blance in  the  wings  of  Birds  and  Insects.  In 


52  CLASSIFICATION  AND   CREATION. 

Birds,  wings  are  a  typical  feature,  corresponding 
to  the  front  limbs  in  all  Vertebrates,  which  are 
constructed  in  the  same  way,  whether  they  are 
arms  as  in  Man,  or  fore-legs  as  in  Quadrupeds,  or 
pectoral  fins  as  in  Fishes,  or  wings  as  in  Birds. 
The  wing  in  an  Insect,  on  the  contrary,  is  a 
flattened,  dried-up  gill,  having  no  structural  re- 
lation whatever  to  the  wing  of  a  Bird.  They 
are  analogous  only,  because  they  resemble  each 
other  in  form  and  in  function,  being  in  the  same 
way  subservient  to  flight;  but  as  organs  they 
are  entirely  different.  The  wings  of  Birds  are 
homologous  to  the  limbs  of  other  Vertebrates, 
notwithstanding  their  great  apparent  difference ; 
they  are  only  analogous  to  the  wings  of  Insects, 
notwithstanding  their  great  external  resemblance. 
In  adding  Infusoria  to  the  Radiates,  Cuvier 
was  false  to  his  own  principle  of  founding  all 
classification  on  plan.  He  was  influenced  by- 
their  seeming  simplicity  of  structure,  and  placed 
them  in  the  lowest  division  of  the  Animal  King- 
dom on  that  account.  But  even  this  simplicity 
was  only  apparent  in  many  of  them.  At  cer- 
tain seasons  of  the  year  myriads  of  these  little 
Animalcules  may  be  seen  in  every  brook  and 
road-side  pool.  They  are  like  transparent  little 
globules,  without  any  special  organization,  appar- 
ently ;  and  were  it  not  that  they  are  in  constant 
rotation,  exhibiting  thus  a  motion  of  their  own, 


CLASSIFICATION  AND   CEEATION.  53 

one  would  hardly  suspect  that  they  were  endowed 
with  life.  To  the  superficial  observer  they  all 
look  alike,  and  it  is  not  strange,  that,  before  they 
had  been  more  carefully  investigated,  they  should 
have  been  associated  together  as  the  lowest  divis- 
ion of  the  Animal  Kingdom,  representing,  as  it 
were,  a  border-land  between  animal  and  vegeta- 
ble life.  But  since  the  modern  improvements  in 
the  microscope,  Ehrenberg,  the  great  master  in 
microscopic  investigation,  has  shown  that  many 
of  these  little  globules  have  an  extraordinary 
complication  of  structure.  Subsequent  investi- 
gations have  proved  that  they  include  a  great 
variety  of  beings :  some  of  them  belonging  to  the 
type  of  Mollusks ;  others  to  the  type  of  Articu- 
lates, being  in  fact  little  shrimps ;  while  many 
others  are  the  locomotive  germs  of  plants,  and  so 
far  from  forming  a  class  by  themselves,  as  a  dis- 
tinct group  in  the  Animal  Kingdom,  they  seem 
to  comprise  not  only  representatives  of  all  types, 
except  Vertebrates,  but  to  belong  also  in  part  to 
the  Vegetable  Kingdom. 

Siebold,  Leuckart,  and  other  modern  zoolo- 
gists, have  considered  them  as  a  primary  type, 
and  called  them  Protozoa ;  but  this  is  as  great  a 
mistake  as  the  other.  The  rotatory  motion  in 
them  all  is  produced  by  an  apparatus  that  exists 
not  only  in  all  animals,  but  in  plants  also,  and  is 
a  most  important  agent  in  sustaining  the  fresh- 


54  CLASSIFICATION   AND   CREATION. 

ness  and  vitality  of  their  circulating  fluids  and 
of  the  surrounding  medium  in  which  they  live. 
It  consists  of  soft  fringes,  called  vibratile  cilia. 
Such  fringes  cover  the  whole  surface  of  these 
little  living  beings,  and  by  their  unceasing  play 
they  maintain  the  rotating  motion  that  carries 
them  along  in  the  water. 

The  Mollusks,  the  next  great  division  of  the 
Animal  Kingdom,  also  include  three  classes. 
With  them  is  introduced  that  character  of  bilat- 
eral symmetry,  or  division  of  parts  on  either  side 
of  a  longitudinal  axis,  that  prevails  throughout 
the  Animal  Kingdom,  with  the  exception  of  the 
Radiates.  The  lowest  class  of  Mollusks  has  been 
named  Acephala,  to  signify  the  absence  of  any 
distinct  head  ;  for  though  their  whole  organiza- 
tion is  based  upon  the  principle  of  bilateral 
symmetry,  it  is  nevertheless  very  difficult  to 
determine  which  is  the  right  side  and  which  the 
left  in  these  animals,  because  there  is  so  little 
prominence  in  the  two  ends  of  the  body  that  the 
anterior  and  posterior  extremities  are  hardly  to 
be  distinguished.  Take  the  oyster  as  an  exam- 
ple. It  has,  like  most  Acephala,  a  shell  with  two 
valves  united  by  a  hinge  on  the  back,  one  of  these 
valves  being  thick  and  swollen,  while  the  other  is 
nearly  flat.  If  we  lift  the  shell,  we  find  beneath 
a  soft  lining  skin  covering  the  whole  animal,  and 
called  by  naturalists  the  mantle,  from  the  inner 


CLASSIFICATION  AND   CREATION.  55 

surface  of  which  arises  a  double  row  of  gills, 
forming  two  pendent  folds  on  the  sides  of  the 
body.  At  one  end  of  the  body  these  folds  do 
not  meet,  but  leave  an  open  space,  where  is  the 
aperture  we  call  the  mouth.  This  is  the  only 
indication  of  an  anterior  extremity ;  but  it  is 
enough  to  establish  a  difference  between  the 
front  and  hind  ends  of  the  body,  and  to  serve  as 
a  guide  in  distinguishing  the  right  and  left  sides. 
If  now  we  lift  the  mantle  and  gills,  we  find  the 
principal  organs  beneath :  the  stomach,  with  a 


Common  Fresh-water  Mussel,  TJnio,  cut  transversely :   a,  fqot ;  b  ft,  gills ; 
c,  mantle  5  d,  shell ;  e,  heart ;  /,  main  cavity,  with  intestines. 

winding  alimentary  canal ;  the  heart  and  liver  ; 
the  bloodvessels,  branching  from  either  side  of 
the  heart  to  join  the  gills  ;  and  a  fleshy  muscle 
passing  from  one  valve  of  the  shell  to  the  other, 
enabling  the  animal  by  its  dilation  or  contraction 
to  open  and  close  its  shell  at  will.  A  cut  across 


56  CLASSIFICATION  AND   CREATION. 

an  animal  of  this  class  shows  very  distinctly  the 
bilateral  arrangement  of  the  parts.  In  such  a 
section  we  see  the  edge  of  the  two  shells  on  either 
side  ;  within  these  the  edge  of  the  mantle  ;  then 
the  double  rows  of  gills  ;  and  in  the  middle  the 
alimentary  canal,  the  heart,  and  the  bloodvessels 
branching  right  and  left.  Some  of  these  animals 
have  eye-specks  on  the  edge  of  the  mantle ;  but 
this  is  not  a  constant  feature.  This  class  of 
Acephala  includes  all  the  Oysters,  Clams,  Mus- 
sels, and  the  like.  When  named  with  reference 
to  their  double  shells,  they  are  called  Bivalves ; 


Common  Hen-Clam,  Mactra,  in  motion. 

and  with  them  are  associated  a  host  of  less  con- 
spicuous animals,  known  as  Ascidians,  Brachio- 
pods,  and  Bryozoa. 

The  second  class  in  this  type  is  that  of  Gas- 
teropoda, so  named  from  the  fleshy  muscular 
expansion  on  which  they  move,  and  which  is 
therefore  called  a  foot:  a  very  inappropriate 
name  ;  since  it  has  no  relation  or  resemblance  to 
a  foot,  though  it  is  used  as  a  locomotive  organ. 
This  class  includes  all  the  Snails,  Slugs,  Cockles, 


CLASSIFICATION  AND   CKEATION.  57 

Conehs,  Periwinkles,  Whelks,  Limpets,  and  the 
like.  Some  of  them  have  no  solid  covering  ;  but 
the  greater  part  are  protected  by  a  single  shell, 
and  on  this  account  they  are  called  Univalves, 
in  contradistinction  to  the  Acephala  or  Bivalves. 
These  shells,  though  always  single,  differ  from 
each  other  by  an  endless  variety  of  form  and 
color,  —  from  the  flat  simple  shell  of  the  Limpet 


a 

Limpet,  Patella,  cut  transversely :   a,  foot ;   b,  gills  ;  c,  mantle  ;  d,  shell ; 
e,  heart ;  /,  main  cavity,  with  intestines. 

to  the  elaborate  spiral  and  brilliant  hues  of  the 
Cones  and  Cowries.  Different  as  is  their  ex- 
ternal covering,  however,  if  we  examine  the 
internal  structure  of  a  Gasteropod,  we  find  the 
same  general  arrangement  of  parts  that  prevails 
in  the  Acephala,  showing  that  both  belong  to  the 
same  great  division  of  the  Animal  Kingdom. 
The  mantle  envelops  the  animal,  and  lines  its 
single  shell  as  it  lined  the  double  shell  of  the 
Oyster ;  the  gills  are  placed  on  either  side  of  it ; 
the  stomach,  with  the  winding  alimentary  canal, 
is  in  the  centre  of  the  body  ;  the  heart  and  liver 
are  placed  in  the  same  relation  to  it  as  in  the 
Acephala ;  and  though  the  so-called  foot  would 
seem  to  be  a  new  feature,  it  is  but  a  muscular 

3* 


58  CLASSIFICATION   AND   CREATION. 

expansion  of  the  ventral  side  of  the  body,  already 
well  developed  in  the  Mussels  and  Clams.  There 
is  an  evident  superiority  in  this  class  over  the 
preceding  one,  in  the  greater  prominence  of  the 
anterior  extremity,  where  there  are  two  or  more 
feelers,  with  which  eyes  more  or  less  developed 
are  connected  ;  and  though  there  is  nothing  that 
can  be  properly  called  a  head,  yet  there  can  be 
no  hesitation  as  to  the  distinction  between  the 
front  and  hind  ends  of  the  body. 


Margarita  arctica,  of  the  coast  of  New  England. 

The  third  and  highest  class  of  Mollusks  has 
been  called  Cephalopoda,  in  reference  again  to  a 
special  feature  of  their  structure.  They  have 
long  arms  or  feelers  around  the  head,  serving  as 
organs  of  locomotion,,  by  which  they  propel  them- 
selves through  the  water  with  a  velocity  that  is 
quite  extraordinary,  when  compared  with  the 
sluggishness  of  the  other  Mollusks.  In  these 
animals  the  head  is  distinctly  marked,  —  being 
separated,  by  a  contraction  or  depression  behind 
it,  from  the  rest  of  the  body.  The  feelers,  so 
prominent  on  the  anterior  extremity  of  the  Gas- 
teropoda, are  suppressed  in  Cephalopoda,  and 
the  eyes  are  consequently  brought  immediately 


CLASSIFICATION  AND   CREATION.  59 

on  the  side  of  the  head,  and  are  very  large  in 
proportion  to  the  size  of  the  animal.  A  skin 
corresponding  to  the  mantle  envelops  the  body, 
and  the  gills  are  on  either  side  of  it ;  —  the 
stomach  with  its  winding  canal,  the  liver,  and 
heart  occupy  the  centre  of  the  body,  as  in  the 
other  two  classes.  This  class  includes  all  the 
Cuttle-Fishes,  Squids,  and  Nautili,  and  has  a 


a 

Common  Squid,  Loligo,  cut  transversely  :  a,  foot  or  siphon  ;  ft,  gills  ;  c,  man- 
tle ;  d,  internal  shell ;  e,  heart ;  /,  main  cavity,  with  intestines. 

vast  number  of  fossil  representatives.     Many  of 
these  animals  are  destitute  of  any  shell ;  and, 


Common  Squid,  Loligo,  in  a  swimming  attitude.- 

with  a  single  exception,  when  they  have  a  shell, 
it  is  not  coiled  from  right  to  left  or  from  left 
to  right,  as  in  the  spiral  of  the  Gasteropoda,  but 
from  behind  forwards,  as  in  the  Nautilus.  These 
shells  are  usually  divided  into  a  number  of 
chambers,  —  the  animal,  as  it  grows,  building  a 
wall  behind  it  at  regular  intervals,  and  always 
occupying  the  external  chamber,  retaining, 


60  CLASSIFICATION  AND   CREATION. 

however,  a  connection  with  his  past  home  by  a 
siphon  that  runs  through  the  whole  succession 
of  chambers.  The  readers  of  the  "  Atlantic 
Monthly  "  cannot  fail  to  remember  the  exquisite 
poem  suggested  to  the  Autocrat  of  the  Break- 
fast-Table by  this  singular  feature  in  the  struc- 
ture of  the  so-called  Chambered  Shells. 

Cuvier  divided  the  Mollusks  also  into  a  larger 
number  of  classes  than  are  now  admitted.  He 
placed  the  Barnacles  with  them,  on  account  of 
their  shells ;  and  it  is  only  since  an  investigation 
of  the  germs  born  from  these  animals  has  shown 
them  to  be  Articulates  that  their  true  position  is 
understood.  They  give  birth  to  little  Shrimps 
that  afterwards  become  attached  to  the  rocks 
and  then  assume  the  shelly  covering  that  has 
misled  naturalists  about  them.  They  ought 
therefore  to  be  referred  to  the  class  of  Crus- 
tacea, in  which  they  are  now  generally  included. 
Brachiopods  formed  another  of  his  classes ;  but 
these  differ  from  the  other  Bivalves  only  in 
having  a  network  of  bloodvessels  upon  their 
mantle,  in  the  place  of  free  gills,  and  this  is 
merely  a  complication  of  structure,  not  a  differ- 
ence in  the  general  mode  of  execution,  for  the 
position  and  relation  of  these  organs  to  the  rest 
of  the  structure  are  exactly  the  same  in  both. 
Pteropods  constituted  another  class  in  his  divis- 
ion of  the  type  of  Mollusks ;  but  these  animals, 


CLASSIFICATION  AND   CREATION.  61 

again,  form  only  an  order  in  the  class  of  Gas- 
teropoda, as  Brachiopods  form  an  order  in  the 
class  of  Acephala. 

In  the  third  division  of  the  Animal  Kingdom, 
the  Articulates,  we  have  again  three  classes: 
Worms,  Crustacea,  and  Insects.  The  lowest  of 
these  three  classes,  the  Worms,  presents  the 
typical  structure  of  that  branch  in  the  most 
uniform  manner,  with  little  individualization  of 
parts.  The  body  is  a  long  cylinder  divided 
through  its  whole  length  by  movable  joints, 
while  the  head  is  indicated  only  by  a  difference 
in  the  front  joints.  There  is  here  no  concentra- 
tion of  vitality  in  special  parts  of  the  structure, 
as  in  the  higher  animals,  but  the  nervous  force  is 
scattered  through  the  whole  body,  —  every  ring 
having,  on  its  lower  side,  either  two  nervous 
swellings,  one  on  the  right,  the  other  on  the  left 
side,  connected  by  nervous  threads  with  those 
that  precede  and  those  that  follow  them,  or  these 
swellings  are  united  in  the  median  line.  It  is  to 
this  equal  distribution  of  nervous  force  through 
the  whole  system  that  these  animals  owe  their 
extraordinary  power  of  repairing  any  injured 
part,  so  that,  if  cut  in  two,  the  front  part  may 
even  reconstruct  a  tail  for  itself,  while  the  hind 
part  produces  a  new  head,  and  both  continue  to 
live  as  distinct  animals.  This  facility  of  self- 
repair,  after  a  separation  of  the  parts,  which  is 


62  CLASSIFICATION  AND   CREATION. 

even  a  normal  mode  of  multiplication  in  some  of 
them,  does  not  indicate,  as  may  at  first  appear,  a 
greater  intensity  of  vital  energy,  but,  on  the  con- 
trary, arises  from  an  absence  of  any  one  nervous 
centre  such  as  exists  in  all  the  higher  animals, 
and  is  the  key  to  their  whole  organization.  A 
serious  injury  to  the  brain  of  a  Vertebrate  de- 
stroys vitality  at  once,  for  it  holds  the  very 
essence  of  its  life  ;  whereas  in  many  of  the  lower 
animals  any  part  of  the  body  may  be  destroyed 
without  injury  to  the  rest.  The  digestive  cavity 
in  the  Worms  runs  the  whole  length  of  the  body ; 
and  the  respiratory  organs,  wherever  they  are 
specialized,  appear  as  little  vesicles  or  gill-like 
appendages  either  along  the  back  or  below  the 
sides,  connected  with  the  locomotive  appen- 
dages. 

This  class  includes  animals  of  various  degrees 
of  complication  of  structure,  from  those  with 
highly  developed  organizations  to  the  Worms 
that  float  in  fresh  water  like  long  hairs  and 
hardly  seem  to  be  animals,  and  to  those  still 
lower  representatives  of  the  class  that  live  in  the 
cavities  of  other  animals.  Yet  even  creatures 
so  low  in  the  scale  of  life  as  the  Gordius,  that 
long  thread-like  Worm  found  often  in  brooks 
and  called  Horsehair  by  the  common  people,  are 
not  devoid  of  some  instincts,  however  dim,  of 
feeling  and  affection.  I  remember  a  case  in 


CLASSIFICATION  AND   CREATION.  63 

point,  that  excited  my  own  wonder  at  the  time, 
and  may  not  be  uninteresting  to  my  readers. 

I  had  received  from  Detroit,  through  the  kind- 
ness of  Messrs.  Higby  and  Stearns,  one  of  these 
singular  animals.  When  I  first  saw  it,  it  was 
coiled  up  in  a  close  roll  at  the  bottom  of  a 
bottle  filled  with  fresh  water,  and  looked  more 
like  a  little  tangle  of  black  sewing-silk  than  any- 
thing else.  Wishing  to  unwind  it,  that  I  might 
examine  its  entire  length,  I  placed  it  in  a  large 
china  basin  filled  with  water,  and  proceeded  very 
gently  to  disentangle  its  coils,  when  I  perceived 
that  the  animal  had  twisted  itself  around  a  bun- 
dle of  its  eggs,  holding  them  fast  in  a  close  em- 
brace. In  the  process  of  unwinding,  the  eggs 
dropped  away  and  floated  to  a  little  distance. 
Having  finally  stretched  it  out  to  its  full  length, 
perhaps  half  a  yard,  I  sat  watching  to  see  if  this 
singular  being  that  looked  like  a  long  black 
thread  in  the  water  would  give  any  signs  of  life. 
Almost  immediately  it  moved  towards  the  bun- 
dle of  eggs,  and,  having  reached  it,  began  to  sew 
itself  through  and  through  the  little  white  mass, 
passing  one  end  of  its.  body  through  it,  and  then 
returning  to  make  another  stitch,  as  it  were,  till 
the  eggs  were  at  last  completely  entangled  again 
in  an  intricate  network  of  coils. 

It  seemed  to  me  almost  impossible  that  this 
care  of  offspring  could  be  the  result  of  any  in- 


64  CLASSIFICATION  AND   CREATION. 

stinct  of  affection  in  a  creature  of  so  low  an 
organization,  and  I  again  separated  it  from  the 
eggs,  and  placed  them  at  a  greater  distance, 
when  the  same  action  was  repeated.  On  trying 
the  experiment  a  third  time,  the  bundle  of  eggs 
had  become  loosened,  and  a  few  of  them  dropped 
off  singly  into  the  water.  The  efforts  which  the 
animal  then  made  to  recover  the  missing  ones, 
winding  itself  round  and  round  them,  but  failing 
to  bring  them  into  the  fold  with  the  rest,  because 
they  were  too  small  and  evaded  all  efforts  to 
secure  them  when  once  parted  from  the  first 
little  compact  mass,  convinced  me  that  there  was 
a  definite  purpose  in  its  attempts,  and  that  even 
a  being  so  low  in  the  scale  of  animal  existence 
has  some  dim  consciousness  of  a  relation  to  its 
offspring. 

I  afterwards  unwound  the  mass  of  eggs,  which, 
when  coiled  up  as  I  first  saw  it,  made  a  roll  of 
white  substance  about  the  size  of  a  coffee-bean, 
and  found  that  it  consisted  of  a  string  of  eggs, 
measuring  more  than  twelve  feet  in  length,  the 
eggs  being  held  together  by  some  gelatinous 
substance  that  cemented  them  and  prevented 
them  from  falling  apart.  Cutting  this  string 
across,  and  placing  a  small  section  under  the 
microscope,  I  counted  on  one  surface  of  such  a 
cut  from  seventy  to  seventy-five  eggs ;  and,  esti- 
mating the  entire  number  of  eggs  according  to 


CLASSIFICATION  AND   CREATION.  65 

the  number  contained  011  such  a  surface,  I  found 
that  there  were  not  less  than  eight  millions  of 
eggs  in  the  whole  string.  The  fertility  of  these 
lower  animals  is  truly  amazing,  and  is  no  doubt 
a  provision  of  Nature  against  the  many  chances 
of  destruction  to  which  these  germs,  so  delicate 
and  often  microscopically  small,  must  be  exposed. 
The  higher  we  rise  in  the  Animal  Kingdom,  the 
more  limited  do  we  find  the  number  of  progeny, 
and  the  care  bestowed  upon  them  by  the  parents 
is  in  proportion  to  this  diminution. 

The  subsequent  adventures  of  these  germs 
form  so  odd  a  sequel  to  their  early  history,  that 
I  will  add  it  here.  The  eggs  are  hatched  in  the 
water,  the  embryos  first  making  their  appearance 
as  little  transparent  bodies,  moving  about  by 
means  of  verbratile  cilia.  Their  only  appen- 
dages are  minute  horns  attached  to  one  end  of 
the  body.  Strange  to  say,  their  next  step  in  life 
is  to  creep  into  the  legs  of  grasshoppers  and  bur- 
row their  way  into  the  abdominal  cavity  of  these 
animals,  where  they  undergo  their  further  develop- 
ment as  Worms,  sometimes  growing  to4  be  two  or 
three  inches  in  length  before  they  are  freed. 
When  they  have  grown  so  large  that  the  grass- 
hopper becomes  distended  by  the  size  of  its 
strange  inhabitant,  it  bursts,  the  Worm  is  re- 
leased, and  returns  to  its  aquatic  life.  When 
familiar  with  the  vicissitudes  in  the  life  of  these 


66  CLASSIFICATION   AND   CREATION. 

animals,  one  ceases  to  wonder  that  Nature  should 
make  large  provision  against  the  many  chances 
of  destruction  that  beset  them,  and  one  may 
readily  believe,  that,  of  the  eight  millions  of  eggs 
born  from  one  individual,  a  comparatively  small 
number  survive. 

The  next  class  in  the  type  of  Articulates  is 
that  of  Crustacea,  including  Lobsters,  Crabs,  and 
Shrimps.  It  may  seem  at  first  that  nothing  can 
be  more  unlike  a  Worm  than  a  Lobster ;  but 
a  comparison  of  the  class-characters  shows  that 
the  same  general  plan  controls  the  organization 
in  both.  The  body  of  the  Lobster  is  divided  into 
a  succession  of  joints  or  rings,  like  that  of  the 
Worm ;  and  the  fact  that  the  front  rings  in  the 
Lobster  are  soldered  together,  so  as  to  make  a 
stiff  front  region  of  the  body,  enclosing  the  head 
and  chest,  while  only  the  hind  rings  remain 
movable,  thus  forming  a  flexible  tail,  does  not 
alter  in  the  least  the  general  structure,  which 
consists  in  both  of  a  body  built  of  articulated 
rings.  The  nervous  swellings,  which  were  even- 
ly distributed  through  the  whole  body  in  the 
Worm,  are  more  concentrated  here,  in  accord- 
ance with  the  prevalent  combination  of  the  rings 
in  two  distinct  regions  of  the  body,  the  larger 
ones  corresponding  to  the  more  important  or- 
gans ;  but  their  relation  to  the  rest  of  the  organ- 
ization, and  their  connection  by  nervous  threads 


CLASSIFICATION  AND   CREATION.  67 

with  each  other,  remain  the  same.  The  respi- 
ratory organs,  which  in  most  of  the  Worms  were 
mere  vesicles  on  the  lower  part  of  the  sides  of 
the  body,  are  here  more  highly  organized  gills  ; 
but  their  general  character  and  relation  to  other 
parts  of  the  structure  are  unchanged,  and  there 
is  a  connection  between  the  gills  and  the  legs 
in  Crustacea,  corresponding  to  that  between  the 
respiratory  organs  in  Worms  and  their  locomo- 
tive appendages.  The  alimentary  canal  consists 
of  a  single  digestive  cavity  passing  through  the 
whole  body,  as  in  Worms,  the  anterior  part  of 
which  is  surrounded  by  a  large  liver.  What  is 
true  of  the  Lobsters  is  true  also,  so  far  as  class- 
characters  are  concerned,  of  all  the  Crustacea. 

Highest  in  this  type  are  the  Insects,  and  among 
these  I  include  Spiders  and  Centipedes  as  well  as 
Winged  Insects.  It  is  true  that  the  Centipedes 
have  a  long  uniform  body  like  Worms,  and  the 
Spiders  have  the  body  divided  into  two  regions 
like  the  Crustacea,  while  the  body  in  true  Insects 
lias  three  distinct  regions,  head,  chest,  and  hind- 
body  ;  but,  notwithstanding  this  apparent  differ- 
ence, both  the  former  share  in  the  peculiar 
class-character  that  places  them  with  the  Winged 
Insects  in  one  class,  distinct  from  all  the  other  Ar- 
ticulates. We  have  seen  that  in  the  Worms  the 
respiratory  organs  are  mere  vesicles,  while  in  the 
Crustacea  they  are  more  highly  organized  gills  ; 


68  CLASSIFICATION  AND   CREATION. 

but  in  Centipedes,  Spiders,  and  Winged  Insects 
the  breathing-apparatus  is  aerial,  consisting  of 
air-holes  on  the  sides  of  the  body,  connected 
with  a  system  of  tubes  and  vessels  extending  into 
the  body  and  admitting  air  to  all  parts  of  it. 
In  the  winged  Insects  this  system  is  very  elabo- 
rate, filling  the  body  with  air  to  such  a  degree  as 
to  render  it  exceedingly  light  and  adapted  to  easy 
and  rapid  flight.  The  general  arrangement  of 
parts  is  the  same  in  this  class  as  in  the  two  oth- 
ers, the  typical  character  being  alike  in  all. 

We  come  now  to  the  highest  branch  of  the  An- 
imal Kingdom,  that  to  which  we  ourselves  be- 
long,—  the  Vertebrates.  This  type  is  usually  di- 
vided into  four  classes,  Fishes,  Reptiles,  Birds, 
and  Mammalia ;  and  though  many  naturalists  be- 
lieve that  it  includes  more,  and  I  am  myself  of 
that  opinion,  I  shall  allude  here  only  to  the  four 
generally  admitted  classes,  as  they  are  sufficient 
for  my  present  purpose,  and  will  serve  to  show 
the  characters  upon  which  classes  are  based. 
In  a  former  paper  I  have  explained  in  general 
terms  the  plan  of  structure  of  this  type,  —  a 
backbone,  with  a  solid  arch  above  and  a  solid 
arch  below,  forming  two  cavities  that  contain  all 
the  systems  of  organs,  the  whole  being  surround- 
ed by  the  flesh  and  skin.  Now  whether  a  body 
so  constructed  lie  prone  in  the  water,  like  a 
Fish,  —  or  be  lifted  on  imperfect  legs,  like  a 


CLASSIFICATION  AND   CKEATION.  69 

Reptile,  —  or  be  balanced  on  two  legs,  while  the 
front  limbs  become  wings,  as  in  Birds,  —  or  be 
raised  upon  four  strong  limbs  terminating  in  paws 
or  feet,  as  in  Quadrupeds,  —  or  stand  upright 
with  head  erect,  while  the  limbs  consist  of  a  pair 
of  arms  and  a  pair  of  legs,  as  in  Man,  —  does  not 
in  the  least  affect  that  structural  conception  un- 
der which  they  are  all  included.  Every  Verte- 
brate  has  a  backbone  ;  every  Vertebrate  has  a 
solid  arch  above  that  backbone  and  a  solid  arch 
below  it,  forming  two  cavities, — no  matter 
whether  these  arches  be  of  hard  bone,  or  of  carti- 
lage, or  even  of  a  softer  substance ;  every  Verte- 
brate has  the  brain,  the  spinal  marrow  or  spinal 
cord,  and  the  organs  of  the  senses  in  the  upper 
cavity,  and  the  organs  of  digestion,  respiration, 
circulation,  and  reproduction,  in  the  lower  one; 
every  Vertebrate  has  four  locomotive  appendages 
built  of  the  same  bones  and  bearing  the  same  re- 
lation to  the  rest  of  the  organization,  whether 
they  be  called  pectoral  and  ventral  fins,  or  legs, 
or  wings  and  legs,  or  arms  and  legs.  Notwith- 
standing the  rudimentary  condition  of  these  limbs 
in  some  Vertebrates  and  their  difference  of  ex- 
ternal appearance  in  the  different  groups,  they 
are  all  built  of  the  same  structural  elements. 
And  even  where  they  seem  wanting,  as  in  Ser- 
pents, a  minute  study  of  the  gradual  reduction 
of  the  locomotive  appendages  in  various  groups 


70  CLASSIFICATION  AND   CREATION. 

of  Reptiles  will  show  that  they  too  are  true  to 
this  structural  plan.  These  are  the  typical  char- 
acters of  the  whole  branch,  and  exist  in  all  its 
representatives. 

What  now  are  the  different  modes  of  express- 
ing this  structural  plan  that  lead  us  to  associate 
certain  Vertebrates  together  in  distinct  classes  ? 
Beginning  with  the  lowest  class,  —  the  Fishes  are 
cold-blooded,  they  breathe  through  gills,  and  they 
are  egg-laying ;  in  other  words,  though  they  have 
the  same  general  structure  as  the  other  Verte- 
brates, they  have  a  special  mode  of  circulation, 
respiration,  and  reproduction.  The  Reptiles  are 
also  cold-blooded,  though  their  system  of  circula- 
tion is  somewhat  more  complicated  than  that  of 
the  Fishes ;  they  breathe  through  lungs,  though 
part  of  them  retain  their  gills  through  life ;  and 
they  lay  eggs,  but  larger  and  fewer  ones  than  the 
Fishes,  diminishing  in  number  in  proportion  to 
their  own  higher  or  lower  position  in  their  class. 
They  also  bestow  greater  care  upon  their  offspring 
than  most  of  the  Fishes.  The  Birds  are  warm- 
blooded and  air-breathing,  having  a  double  cir- 
culation ;  they  are  egg-laying,  like  the  two  other 
classes,  but  their  eggs  are  comparatively  few  in 
number,  and  the  young  are  hatched  by  the  moth- 
er and  fed  by  the  parent  birds  till  they  can  pro- 
vide for  themselves. 

The   Mammalia   are    also    warm-blooded    and 


CLASSIFICATION   AND    CKEATION.  71 

breathe  through  lungs ;  but  they  differ  from  all 
other  Vertebrates  in  their  mode  of  reproduction, 
bringing  forth  living  young,  which  they  nurse 
with  milk.  Even  in  the  lowest  members  of  this 
highest  group  of  the  Vertebrates,  at  the  head 
of  which  stands  Man  himself,  looking  heaven- 
ward it  is  true,  but  nevertheless  rooted  deeply  in 
the  Animal  Kingdom,  we  have  the  dawning  of 
those  family  relations,  those  intimate  ties  between 
parents  and  children,  on  which  the  whole  social 
organization  of  the  human  race  is  based.  Man 
is  the  crowning  work  of  God  on  earth ;  but 
though  so  nobly  endowed,  we  must  not  forget 
that  we  are  the  lofty  children  of  a  race  whose 
lowest  forms  lie  prostrate  within  the  water,  hav- 
ing no  higher  aspiration  than  the  desire  for  food  ; 
and  we  cannot  understand  the  possible  degrada- 
tion and  moral  wretchedness  of  Man,  without 
knowing  that  his  physical  nature  is  rooted  in  all 
the  material  characteristics  that  belong  to  his 
type  and  link  him  even  with  the  Fish.  The 
moral  and  intellectual  gifts  that  distinguish  him 
from  them  are  his  to  use  or  to  abuse ;  he  may,  if 
he  will,  abjure  his  better  nature  and  be  Verte- 
brate more  than  Man.  He  may  sink  as  low  as  the 
lowest  of  his  type,  or  he  may  rise  to  a  spiritual 
height  that  will  make  that  which  distinguishes 
him  from  the  rest  far  more  the  controlling  ele- 
ment of  his  being  than  that  which  unites  him 
with  them. 


72  MEANING   OF   ORDERS. 


CHAPTER  V. 

DIFFERENT   VIEWS  RESPECTING   ORDERS. 

IT  is  in  the  search  after  the  true  boundaries 
and  characteristics  of  orders  that  we  may  expect 
the  greatest  advance  by  the  naturalists  of  the 
present  day ;  and  yet  there  is  now  much  discre- 
pancy among  them,  some  mistaking  orders  for 
classes,  others  raising  families  to  the  dignity  of 
orders.  This  want  of  agreement  in  their  results 
is  not  strange,  however ;  for  the  recognition  of 
orders  is  indeed  exceedingly  difficult.  If  they 
are,  as  I  have  denned  them,  groups  in  Nature 
founded  upon  a  greater  or  less  complication  of 
structure,  they  rnus,t,-  of  course,  form  a  regular 
gradation  within  the  limits  of  their  class,  since 
comparative  perfection  implies  comparative  rank, 
and  a  correct  estimate  of  these  degrees  of  com- 
plication requires  an  intimate  and  extensive 
knowledge  of  structure  throughout  the  class. 
There  would  seem  to  be  an  arbitrary  element 
here,  —  that  of  our  individual  appreciation  of 
structural  character.  If  one  man  holds  a  certain 
kind  of  structural  characters  superior  to  another, 


MEANING   OF   ORDERS.  73 

he  will  establish  the  rank  of  the  order  upon  that 
feature,  while  some  other  naturalist,  appreciating 
a  different  point  of  the  structure  more  highly, 
will  make  that  the  test  character  of  the  group. 
Let  us  see  whether  we  can  eliminate  this  arbitra- 
ry element  in  our  estimate  of  these  groups,  and 
find  any  mode  of  determining  orders  that  shall 
be  unquestionable,  and  give  us  results  as  positive 
as  a  chemical  analysis  according  to  quantitative 
elements.  I  believe  that  there  are  such  absolute 
tests  of  structural  relations.  It  is  my  conviction, 
that  orders,  like  all  the  other  groups  of  the 
Animal  Kingdom,  have  a  positive  existence  in 
Nature  with  definite  limits ;  that  no  arbitrary 
element  should  enter  into  any  part  of  our  classi- 
fications ;  and  that  we  have  already  the  key  by 
which  to  solve  this  question  about  orders. 

To  illustrate  this  statement,  I  must  return  to 
the  class  of  Insects.  We  have  seen  that  they 
are  divided  into  three  orders :  the  long  cylindri- 
cal Centipedes,  with  the  body  divided  throughout 
in  uniform  rings,  like  the  worms;  the  Spiders, 
with  the  body  divided  into  two  regions;, and  the 
Winged  Insects,  with  head,  chest,  and  hind  body 
distinct  from  each  other,  forming  three  separate 
regions.  In  the  first  group,  the  Centipedes,  the 
nervous  system  is  scattered  through  the  whole 
body,  as  in  the  Worms ;  in  the  Spiders  it  is  con- 
centrated in  two  nervous  swellings,  as  in  Crusta- 

4 


74  MEANING    OF    ORDERS. 

cea,  the  front  one  being  the  largest ;  and  in  the 
Insects  there  are  three  nervous  centres,  the  larg- 
est in  the  head,  a  smaller  one  in  the  chest,  and 
the  smallest  in  the  hind  body.  Now  according 
to  this  greater  or  less  individualization  of  parts, 
with  the  corresponding  localization  of  the  ner- 
vous centres,  naturalists  have  established  the  rel- 
ative rank  of  these  three  groups,  placing  Centi- 
pedes lowest,  Spiders  next,  and  Winged  Insects 
highest.  But  naturalists  may,  and  indeed  they 
actually  do,  differ  as  to  this  estimation  of  the 
anatomical  structure,  for  the  Spiders  are  placed 
above  Insects  by  some  naturalists,  and  many  even 
consider  them  a  distinct  class.  Have  we,  then, 
any  means  of  testing  its  truth  to  Nature  ?  Let  us 
look  at  the  development  of  these  animals,  taking 
the  highest  order  as  an  illustration,  that  we  may 
have  the  whole  succession  of  changes. 

All  know  the  story  of  the  Butterfly  with  its 
three  lives,  as  Caterpillar,  Chrysalis,  and  Winged 
Insect.  I  speak  of  its  three  lives,  but  we  must 
not  forget  that  they  make  after  all  but  one  life, 
and  that  the  Caterpillar  is  as  truly  the  same  be- 
ing with  the  future  Butterfly,  as  the  child  is  the 
same  being  with  the  future  man.  The  old  signifi- 
cance of  the  word  metamorphosis  —  the  fabled 
transformation  of  one  individual  into  another,  in 
which  so  much  of  the  imagination  and  poetical 
culture  of  the  ancients  found  expression  —  still 


MEANING   OF   ORDERS.  75 

clings  to  us ;  and  where  the  different  phases  of 
the  same  life  assume  such  different  external 
forms,  we  are  apt  to  overlook  the  fact  that  it  is  one 
single  continuous  life.  To  a  naturalist,  metamor- 
phosis is  simply  growth ;  and  in  that  sense  the 
different  stages  of  development  in  animals  that 
undergo  their  successive  changes  within  the  egg 
are  as  much  metamorphoses  as  the  successive 
phases  of  life  in  those  animals  that  complete  their 
development  after  they  are  hatched. 

But  to  return  to  our  Butterfly.  In  its  most 
imperfect,  earliest  condition,  it  is  Worm-like,  the 
body  consisting  of  thirteen  uniform  rings ;  but 
when  it  has  completed  this  stage  of  existence,  it 
passes  into  the  Chrysalis  state,  during  which  the 
body  has  two  regions,  the  front  rings  being  sol- 
dered together  to  form  the  head  and  chest,  while 
the  hind  joints  remain  distinct;  and  it  is  only 
when  it  bursts  from  its  Chrysalis  envelope,  as  a 
complete  Winged  Insect,  that  it  has  three  distinct 
regions  of  the  body.  Do  not  the  different  periods 
of  growth  in  this  highest  order  explain  the  rela- 
tion of  all  the  orders  to  each  other?  The  earliest 
condition  of  an  animal  cannot  be  its  highest  con- 
dition,—  it  does  not  pass  from  a  more  perfect  to 
a  less  perfect  state  of  existence.  The  history  of 
its  growth  is,  on  the  contrary,  the  history  of  its 
progress  in  development;  and  therefore,  when 
we  find  that  the  first  stage  of  growth  in  the 


76  MEANING   OF   ORDERS. 

Winged  Insect  transiently  represents  a  structural 
character  that  is  permanent  in  the  lowest  order 
of  its  class,  that  its  second  stage  of  growth  tran- 
siently represents  a  structural  character  that  is 
permanent  in  the  second  order  of  its  class,  and 
that  only  in  the  last  stage  of  its  existence  does 
the  Winged  Insect  attain  its  complete  and  perfect 
condition,  we  may  fairly  infer  that  this  division 
of  the  class  of  Insects  into  a  gradation  of  orders, 
placing  Centipedes  lowest,  Spiders  next,  and 
Winged  Insects  highest,  is  true  to  Nature. 

This  is  not  the  only  instance  in  which  the  em- 
bryological  evidence  confirms  perfectly  the  ana- 
tomical evidence  on  which  orders  have  been  dis- 
tinguished, and  I  believe  that  Embryology  will 
give  us  the  true  standard  by  which  to  test  the 
accuracy  of  our  ordinal  groups.  In  the  class  of 
Crustacea,  for  instance,  the  Crabs  have  been 
placed  above  the  Lobsters  by  some  naturalists,  in 
consequence  of  certain  anatomical  features ;  but 
there  may  easily  be  a  difference  of  individual 
opinion  as  to  the  relative  value  of  these  features. 
When  we  find,  however,  that  the  Crab,  while  un- 
dergoing its  changes  in  the  egg,  passes  through 
a  stage  in  which  it  resembles  the  Lobster  much 
more  than  it  does  its  own  adult  condition,  we 
cannot  doubt  that  its  earlier  state  is  its  lower  one, 
and  that  the  organization  of  the  Lobster  is  not  as 
high  in  the  class  of  Crustacea  as  that  of  the 


MEANING   OF    ORDERS.  77 

Crab.  While  using  illustrations  of  this  kind, 
however,  I  must  guard  against  misinterpretation. 
These  embryological  changes  are  never  the  pass- 
ing of  one  kind  of  animal  into  another  kind  of 
animal ;  the  Crab  is  none  the  less  a  Crab  during 
that  period  of  its  development  in  which  it  resem- 
bles a  Lobster ;  it  simply  passes,  in  the  natural 
course  of  its  growth,  through  a  phase  of  ex- 
istence which  is  permanent  in  the  Lobster,  but 
transient  in  the  Crab.  Such  facts  should  stimu- 
late all  our  young  students  to  embryological 
investigation,  as  a  most  important  branch  of 
study  in  the  present  state  of  our  science. 

But  while  there  is  this  structural  gradation 
among  orders,  establishing  a  relative  rank  be- 
tween them,  are  classes  and  branches  also  linked 
together  as  a  connected  chain  ?  That  such  a 
chain  exists  throughout  the  Animal  Kingdom 
has  long  been  a  favorite  idea,  not  only  among 
naturalists,  but  also  in  the  popular  mind.  Lam- 
arck was  one  of  the  greatest  teachers  of  this 
doctrine.  He  held,  not  only  that  branches  and 
classes  were  connected  in  a  direct  gradation,  but 
that  within  each  class  there  was  a  regular  series 
of  orders,  families,  genera,  and  species,  forming 
a  continuous  chain  from  the  lowest  animals  to 
the  highest,  and  that  the  whole  had  been  a  grad- 
ual development  of  higher  out  of  lower  forms. 
I  have  already  alluded  to  his  division  of  the 


78  MEANING   OF   OKDERS. 

Animal  Kingdom  into  the  Apathetic,  Sensitive, 
and  Intelligent  animals.  The  Apathetic  were 
those  devoid  of  all  sensitiveness  except  when 
aroused  by  the  influence  of  some  external  agent. 
Under  this  head  he  placed  five  classes,  includ- 
ing the  Infusoria,  Polyps,  Star-Fishes,  Sea-Ur- 
chins,  Tunicata,  and  Worms,  —  thus  bringing 
together  indiscriminately  Radiates,  Mollusks,  and 
Articulates.  Under  the  head  of  Sensitive  he 
had  also  a  heterogeneous  assemblage,  including 
Winged  Insects,  Spiders,  Crustacea,  Annelids, 
and  Barnacles,  all  of  which  are  Articulates,  and 
with  these  he  placed  in  two  classes  the  Mollusks, 
Conchifera,  Gasteropoda,  and  Cephalopoda.  Un- 
der the  head  of  Intelligent  he  brought  together  a 
natural  division,  for  he  here  united  all  the  Ver- 
tebrates. 

He  succeeded  in  this  way  in  making  out  a 
series  which  seemed  plausible  enough,  but  when 
we  examine  it,  we  find  at  once  that  it  is  perfectly 
arbitrary ;  for  he  has  brought  together  animals 
built  on  entirely  different  structural  plans,  when 
he  could  find  characters  among  them  that  seemed 
to  justify  his  favorite  idea  of  a  gradation  of  qual- 
ities. Blainville  attempted  to  establish  the  same 
idea  in  another  way.  He  founded  his  series  on 
gradations  of  form,  placing  together  in  one  divis- 
ion all  animals  that  he  considered  vague  and  in- 
definite in  form,  and  in  another  all  those  that  he 


MEANING   OF   ORDERS.  79 

considered  symmetrical.  Under  a  third  head  he 
brought  together  the  Kadiates ;  but  his  symmet- 
rical division  united  Articulates,  Mollusks,  and 
Vertebrates  in  the  most  indiscriminate  manner. 
He  sustained  his  theory  by  assuming  intermediate 
groups,  —  as,  for  instance,  the  Barnacles  be- 
tween the  Mollusks  and  Articulates,  whereas 
they  are  as  truly  Articulates  as  Insects  or  Crabs. 
Thus,  by  misplacing  certain  animals,  he  arrived 
at  a  series  which,  like  that  of  Lamarck,  made  a 
strong  impression  on  the  scientific  world,  till  a 
more  careful  investigation  of  facts  exposed  its 
fallacy. 

Okeiij  the  great  German  naturalist,  also  at- 
tempted to  establish  a  connected  chain  through- 
out the  Animal  Kingdom,  but  on  an  entirely 
different  principle ;  and  I  cannot  allude  to  this 
most  original  investigator,  so  condemned  by  some, 
so  praised  by  others,  so  powerful  in  his  influence 
on  science  in  Germany,  without  attempting  to 
give  some  analysis  of  his  peculiar  philosophy. 
For  twenty  years  his  classification  was  accepted 
by  his  countrymen  without  question  ;  and  though 
I  believe  it  to  be  wrong,  yet,  by  the  ingenuity 
with  which  he  maintained  it,  he  has  shed  a  flood 
of  light  upon  science,  and  has  stimulated  other 
naturalists  to  most  important  and  interesting  in- 
vestigations. 

This  famous  classification  was   founded  upon 


80  MEANING   OF   OHDEES. 

the  idea  that  the  system  of  man,  the  most  perfect 
created  being,  is  the  measure  for  the  whole  Ani- 
mal Kingdom,  and  that  in  analyzing  his  organi- 
zation we  have  the  clew  to  all  organized  beings. 
The  structure  of  man  includes  two  systems  of 
organs :  those  which  maintain  the  body  in  its  in- 
tegrity, and  which  he  shares  in  some  sort  with 
the  lower  animals,  —  the  organs  of  digestion,  cir- 
culation, respiration,  and  reproduction  ;  and  that 
higher  system  of  organs,  the  brain,  spinal  mar- 
row, and  nerves,  with  the  organs  of  sense,  on 
which  all  the  manifestations  of  the  intelligent 
faculties  depend,  and  by  which  his  relations  to 
the  external  world  are  established  and  controlled : 
the  whole  being  supported  by  a  solid  bony  frame 
and  surrounded  by  flesh,  muscles,  and  skin.  On 
account  of  this  fleshy  envelope  of  the  hard  parts 
in  all  the  higher  animals,  Oken  divided  the  Ani- 
mal Kingdom  into  two  groups,  the  Vertebrates 
and  Invertebrates,  pr,  as  he  called  them,  the 
"  Eingeweide  und  Fleisch-Thiere" —  which  we 
may  translate  as  the  Intestinal  Animals,  or  those 
that  represent  the  intestinal  systems  of  organs, 
and  the  Flesh  Animals,  or  those  that  combine  all 
the  systems  of  organs  under  one  envelope  of 
flesh.  Let  us  examine  a  little  more  closely  this 
singular  theory,  by  which  each  branch  of  the  In- 
vertebrates becomes,  as  it  were,  the  exponent  of 
a  special  system  of  organs,  while  the  Vertebrates, 


MEANING   OF    OKDERS.  81 

with  man  at  their  head,  include  all  these  sys- 
tems. 

According  to  Oken,  the  Radiates,  the  lowest 
type  of  the  Animal  Kingdom,  embody  digestion. 
They  all  represent  a  stomach,  whether  it  is  the 
simple  sac  of  the  Polyps,  or  the  cavity  of  the 
Acalephs,  with  its  radiating  tubes  traversing  the 
gelatinous  mass  of  the  body,  or  the  cavity  and 
tubes  of  the  Echinoderms,  enclosed  within  walls 
of  their  own. 

The  Mollusks  represent  circulation ;  and  his 
division  of  this  type  into  classes,  according  to 
what  he  considers  the  higher  or  lower  organ- 
ization of  the  heart,  agrees  with  the  ordinary 
division  into  Acephala,  Gasteropoda,  and  Cepha- 
lopoda. 

The  Articulates  are  the  respiratory  animals  in 
this  classification:  they  represent  respiration. 
The  Worms,  breathing,  as  he  asserts,  through  the 
whole  surface  of  the  skin,  without  special  breath- 
ing organs,  are  the  lowest ;  the  Crustacea,  with 
gills,  or  aquatic  breathing  organs,  come  next; 
and  he  places  the  Insects  highest,  with  their 
branching  tracheae,  admitting  air  to  all  parts  of 
the  body. 

The  Vertebrates,  or  Flesh  Animals,  with  their 
four  classes,  represent  the  Bones,  the  Muscles, 
the  Nerves,  and  the  Organs  of  Sense,  the  Fishes 
being  par  excellence  the  bony  animals,  the  Rep- 

4*  V 


82  MEANING   OF   ORDERS. 

tiles  representing  especially  the  muscular  system, 
the  Birds  the  nervous  system,  while  in  the  Mam- 
malia the  organs  of  the  senses  are  most  highly 
developed. 

This  theory,  according  to  which  there  are  as 
many  great  divisions  or  classes  as  there  are 
structural  systems  or  combinations  of  systems  in 
the  Animal  Kingdom,  seemed  natural  and  signifi- 
cant, and  there  was  something  attractive  in  the 
idea  that  man  represents,  as  it  were,  the  syn- 
thetic combination  of  all  these  different  systems. 
Oken  also,  in  his  exposition  of  his  mode  of 
classification,  showed  an  insight  into  the  struct- 
ure and  relations  of  animals  that  commended  it 
to  the  interest  of  all  students  of  Nature,  and  en- 
titles him  to  their  everlasting  gratitude.  Never- 
theless, his  theory  fails,  when  it  is  compared  with 
facts.  For  instance,  there  are  many  Worms  that 
have  no  respiration  through  the  skin,  while  his 
appreciation  of  the  whole  class  is  founded  on  that 
feature ;  and  in  his  type  representing  circulation, 
the  Mollusks,  there  are  those  that  have  no  heart 
at  all. 

It  would  carry  me  too  far  into  scientific  details, 
were  I  to  explain  all  the  points  at  which  this 
celebrated  classification  fails.  Suffice  it  to  say, 
that  there  is  no  better  proof  of  the  discrepancy 
between  the  system  and  the  facts  than  the  con- 
stant changes  in  the  different  editions  of  Oken's 


MEANING   OF   ORDERS. 


own  works  and  in  the  publications  of  his  follow- 
ers founded  upon  his  views,  showing  that  they 
were  themselves  conscious  of  the  shifting  and 
unstable  character  of  their  scientific  ground. 


84  GRADATION  AMONG  ANIMALS. 


CHAPTER  VI- 

GRADATION  AMONG  ANIMALS. 

WHAT,  then,  is  the  relation  of  these  larger 
groups  to  each  other,  if  they  do  not  stand  in  a 
connected  series  from  the  lowest  to  the  highest  ? 
How  far  are  each  of  the  branches  and  each  of 
the  classes  superior  or  inferior  one  to  another  ? 
All  agree,  that,  while  Vertebrates  stand  at 
the  head  of  the  Animal  Kingdom,  Radiates  are 
lowest.  There  can  be  no  doubt  upon  this  point ; 
for,  while  the  Vertebrate  plan,  founded  upon  a 
double  symmetry,  includes  the  highest  possibili- 
ties of  animal  organization,  there  is  a  certain  mo- 
notony of  structure  in*  the  Radiate  plan,  in  which 
the  body  is  divided  into  a  number  of  identical 
parts,  bearing  definite  relations  to  a  central  verti- 
cal axis.  But  while  all  admit  that  Vertebrates 
are  highest  and  Radiates  lowest,  how  do  the  Ar- 
ticulates and  Mollusks  stand  to  these  and  to  each 
other  ?  To  me  it  seems,  that,  while  both  are  de- 
cidedly superior  to  the  Radiates  and  inferior  to 
the  Vertebrates,  we  cannot  predicate  absolute 
superiority  or  inferiority  of  organization  of  either 


GRADATION  AMONG  ANIMALS.  85 

group  as  compared  with  the  other ;  they  stand 
on  one  structural  level,  though  with  different 
tendencies,  —  the  body  in  Mollusks  having  always 
a  soft,  massive,  concentrated  character,  with 
great  power  of  contraction  and  dilatation,  while 
the  body  in  Articulates  is  divided  by  transverse 
articulations,  and  has  nothing  of  this  compact- 
ness and  concentration,  but,  on  the  contrary,  is 
usually  marked  by  a  conspicuous  external  dis- 
play of  limbs  and  other  appendages,  and  by  a  re- 
markable elongation  of  the  body,  —  that  feature 
characterized  by  Baer  when  he  called  them  the 
Longitudinal  type.  There  is  in  the  Articulates 
an  extraordinary  tendency  toward  outward  ex- 
pression singularly  in  contrast  to  the  soft,  con- 
tractile body  of  the  Mollusks.  We  need  only 
remember  the  numerous  Insects  with  small  bod- 
ies and  enormously  large  wings,  or  the  Spiders 
with  little  bodies  and  long  legs,  or  the  number 
and  length  of  the  claws  in  the  Lobsters  and 
Crabs,  as  illustrations  of  this  statement  for  the 
Articulates,  while  the  soft',  compact  body  of  the 
Oyster  or  of  the  Snail  is  equally  characteristic  of 
the  Mollusks ;  and  though  it  may  seem  that  this 
assertion  cannot  apply  to  the  highest  class  of 
Mollusks,  the  Cephalopoda,  including  the  Cuttle- 
Fishes  with  their  long  arms  or  feelers,  yet  even 
these  conspicuous  appendages  have  considera- 
ble power  of  contraction  and  dilatation,  and  in 


86  GRADATION  AMONG  ANIMALS. 

the  Nautili  may  be  drawn  completely  within  the 
shell.  If  this  view  be  correct,  these  two  types 
occupy  an  intermediate  position  between  the 
highest  and  the  lowest  divisions  of  the  Animal 
Kingdom,  but  stand  on  equal  ground  when  com- 
pared with  each  other. 

Another,  though  a  less  direct,  evidence  that 
there  is  no  absolute  structural  superiority  or  in- 
feriority between  these  two  types  as  a  whole 
may  be  found  in  the  fact  that  the  most  pro- 
found naturalists  who  have  attempted  a  serial 
arrangement  of  the  whole  Animal  Kingdom  have 
differed  in-  their  estimate  of  these  two  divisions, 
some  placing  the  Mollusks  highest,  while  others 
have  given  the  ascendency  to  the  Articulates. 

But  is  there  a  transition  from  Radiates  to 
Mollusks,  or  from  Articulates  to  Vertebrates,  or 
from  any  one  of  these  divisions  into  any  other  ? 
Let  us  first  consider  the  classes  as  they  stand 
within  their  divisions.'  We  have  seen  that  there 
are  three  classes  of  Radiates,  —  Polyps,  Acalephs, 
and  Echinoderms ;  three  classes  of  Mollusks,  — 
Acephala,  Gasteropoda,  and  Cephalopoda ;  three 
classes  of  Articulates,  —  Worms,  Crustacea,  and 
Insects ;  and,  according  to  the  usually  accepted 
classification,  four  classes  of  Vertebrates, — 
Fishes,  Reptiles,  Birds,  and  Mammalia.  If  there 
is  indeed  a  transition  between  all  these  classes, 
it  must  become  clear  to  us,  when  we  have  accu- 
rately interpreted  their  relative  standing. 


GRADATION  AMONG  ANIMALS.  87 

Taking  first,  then,  the  lowest  branch,  how  do 
the  classes  stand  within  the  limits  of  the  type  of 
Radiates  ?  I  think  I  have  said  enough  of  these 
different  classes  to  show  that  Polyps  as  a  whole 
are  inferior  to  the  Acalephs  as  a  whole,  and  that 
Acalephs  as  a  whole  are  inferior  to  Echinoderms 
as  a  whole.  But  if  they  are  linked  together  as  a 
connected  series,  then  the  lowest  Acaleph  should 
stand  next  in  structure  above  the  highest  Polyp ; 
and  the  lowest  Echinoderm  next  above  the  high- 
est Acaleph.  So  far  from  this  being  the  case, 
there  are,  on  the  contrary,  many  Acalephs  which, 
in  their  specialization,  are  unquestionably  lower 
in  the  scale  of  life  than  some  Polyps,  while 
there  are  some  Echinoderms  lower  in  the  same 
sense  than  many  Acalephs. 

This  remark  applies  equally  to  the  classes 
within  the  other  types  ;  they  stand,  as  an  average, 
relatively  to  each  other,  lower  and  higher,  but, 
considered  in  their  diversified  specification,  there 
are  some  members  of  the  higher  classes  that  are 
inferior  in  organization  to  some  members  of  the 
lower  classes.  The  same  is  true  of  the  great  di- 
visions as  compared  with  each  other.  Instead  of 
the  highest  Radiates  being  always  lower  in  organ- 
ization than  the  lowest  Mollusks,  there  are  many 
Star-Fishes  and  Sea-Urchins  higher  in  organiza- 
tion than  some  Mollusks ;  and  so  when  we  pass 
from  this  branch  to  the  Articulates,  if  we  assume 


88  GRADATION  AMONG  ANIMALS. 

for  the  moment,  as  some  naturalists  believe,  that 
the  Mollusks  are  the  inferior  type,  the  Cuttle- 
Fishes  are  certainly  very  superior  animals  to 
most  of  the  Worms ;  and  passing  from  Articu- 
lates to  Vertebrates,  not  only  are  there  Insects  of 
a  more  complex  organization  than  the  lowest 
Fishes,  but  we  bring  together  two  kinds  of  ani- 
mals so  remote  from  each  other  in  structure  that 
the  wildest  imagination  can  scarcely  fancy  a  tran- 
sition between  them. 

A  comparison  may  make  my  meaning  clearer 
as  to  the  relative  standing  of  these  groups.  The 
Epic  Poem  is  a  higher  order  of  composition  than 
the  Song,  —  yet  we  may  have  an  Epic  Poem 
which,  from  its  inferior  mode  of  execution, 
stands  lower  than  a  Song  that  is  perfect  of  its 
kind.  So  the  plan  of  certain  branches  is  more 
comprehensive  and  includes  higher  possibilities 
than  that  of  others,  while  at  the  same  time  there 
may  be  species  in  which  the  higher  plan  is  exe- 
cuted in  so  simple  a  manner  that  it  places  their 
organization  below  some  more  highly  developed 
being  built  on  a  lower  plan.  It  is  a  poor  com- 
parison, because  everything  that  God  has  made 
is  perfect  of  its  kind  and  in  its  place,  though  rel- 
atively lower  or  higher ;  yet  it  is  only  by  compar- 
ison of  what  is,  after  all,  akin,  —  of  mind  with 
mind,  —  even  though  so  far  apart  as  the  works 
of  the  divine  and  the  human  reason,  that  we 


GRADATION   AMONG  ANIMALS. 


89 


may   arrive   at   some  idea,  however   dim,  of  the 
mental  operations  of  the  Creative  Intellect. 

It  is,  then,  in  their  whole  bulk  that  any  of 
these  groups  is  above  any  other.  We  may  repre- 
sent the  relative  positions  of  the  classes  by  a  dia- 
gram in  which  each  successive  class  in  every  type 
starts  at  a  lower  point  than  that  at  which  the 
preceding  class  closes.  Taking  the  Polyps  as  the 
lowest  class  of  Kadiates,  for  instance,  its  highest 
animals  rise  above  the  lowest  members  of  the 
Acalephs,  but  then  the  higher  members  of  the 
class  of  Acalephs  reach  a  point  far  above  any  of 
the  Polyps,  —  and  so  on. 

RADIATES.       MOLLUSKS.      ARTICULATES.    VERTEBRATES. 


Mammalia. 


Echino- 
derma. 


Acalephs. 
Polyps.  Acephala.  Worms.  Fishes. 


Gas 
pod 

Cepl 
poc 

*ro- 
a. 

2°- 

Crue 

Inse 

acea. 

cts. 

Kept 

Bir 

Ics. 

If  this  view  be  correct,  it  sets  aside  the  possi- 
bility of  any  uninterrupted  series  based  on  abso- 
lute superiority  or  inferiority  of  structure,  on 
which  so  much  ingenuity  and  intellectual  power 
have  been  wasted. 

But  it  is  not  merely  upon  the  structural  rela- 
tions established  between  these  groups  by  ana- 


90  GRADATION  AMONG  ANIMALS. 

tomical  features  in  the  adult  that  we  must  decide 
this  question.  We  must  examine  it  also  from 
the  embryological  point  of  view.  Every  animal 
in  its  growth  undergoes  a  succession  of  changes  : 
is  there  anything  in  these  changes  implying  a 
transition  of  one  type  into  another?  Baer  has 
given  us  the  answer  to  this  question.  He  has 
shown  that  there  are  four  distinct  modes  of  de- 
velopment, as  well  as  four  plans  of  structure ; 
and  though  we  have  seen  that  higher  animals  of 
one  class  pass  through  phases  of  growth  in  which 
they  transiently  resemble  lower  animals  of  the 
same  class,  yet  each  one  of  these  four  modes  of 
development  is  confined  within  the  limits  of  the 
type,  and  a  Vertebrate  never  resembles,  at  any 
stage  of  its  growth,  anything  but  a  Vertebrate, 
or  an  Articulate  anything  but  an  Articulate,  or  a 
Mollusk  anything  but  a  Mollusk,  or  a  Radiate 
anything  but  a  Radiate. 

Yet,  although  therje  is  no  embryological  transi- 
tion of  one  type  into  another,  the  gradations  of 
growth  within  the  limits  of  the  same  type  and  the 
same  class,  already  alluded  to,  are  very  striking 
throughout  the  Animal  Kingdom.  There  are 
periods  in  the  development  of  the  germ  in  the 
higher  members  of  all  the  types,  when  they 
transiently  resemble  in  their  general  outline  the 
lower  representatives  of  the  same  type,  just  as  we 
have  seen  that  the  higher  orders  of  one  class 


GRADATION  AMONG  ANIMALS.  91 

pass  through  stages  of  development  in  which  they 
transiently  resemble  lower  orders  of  the  same 
class.  This  gradation  of  growth  corresponds  to 
the  gradation  of  rank  in  adult  animals,  as  estab- 
lished upon  comparative  complication  of  struct- 
ure. For  instance,  according  to  their  structural 
character,  all  naturalists  have  placed  Fishes  low- 
est in  the  scale  of  Vertebrates.  Now  all  the 
higher  Vertebrates  have  a  Fish-like  character  at 
first,  and  pass  successively  through  phases  in 
which  they  vaguely  resemble  other  lower  forms 
of  the  same  type  before  they  assume  their  own 
characteristic  form ;  and  this  is  equally  true  of 
the  other  great  divisions,  so  that  the  history  of 
the  individual  is,  in  some  sort,  the  history  of  its 
type. 

There  is  still  another  aspect  of  this  question, 
—  that  of  time.  If  neither  the  gradation  of 
structural  rank  among  adult  animals  nor  the 
gradation  of  growth  in  their  embryological  de- 
velopment gives  us  any  evidence  of  a  transition 
between  types,  does  not  the  sequence  of  animals 
in  their  successive  introduction  upon  the  globe 
afford  any  proof  of  such  a  connection  ?  In  this 
relation,  I  must  briefly  allude  to  the  succession 
of  geological  formations  that  compose  the  crust 
of  our  globe.  The  limits  of  this  article  will  not 
allow  me  to  enter  at  any  length  into  the  geologi- 
cal details  connected  with  this  question;  but  I 


92  GRADATION  AMONG  ANIMALS. 

will,  in  the  most  cursory  manner,  give  a  sketch 
of  the  great  geological  periods,  as  generally  ac- 
cepted now  by  geologists. 

The  first  of  these  periods  has  been  called  the 
Azoic  or  lifeless  period,  because  it  is  the  only  one 
containing  stratified  deposits  in  which  there  are 
no  remains  of  organic  life,  and  it  is  therefore 
supposed  that  at  that  early  stage  of  the  world's 
history  the  necessary  conditions  for  the  mainte- 
nance of  animals  and  plants  were  not  yet  estab- 
lished. After  this,  every  great  geological  period 
that  follows  has  been  found  to  be  characterized 
by  a  special  set  of  animals  and  plants,  differing 
from  all  that  follow  and  all  that  precede  it,  till 
we  arrive  at  our  own  period,  when  Man,  with  the 
animals  and  plants  that  accompany  him  on  earth, 
was  introduced. 

There  is,  then,  an  order  of  succession  in  time 
among  animals ;  and  if  there  has  been  any  tran- 
sition between  types  and  classes,  any  growth  of 
higher  out  of  lower  forms,  it  is  here  that  we 
should  look  for  the  evidence  of  it.  According  to 
this  view,  we  should  expect  to  find  in  the  first 
period  in  which  organic  remains  are  found  at  all 
only  the  lowest  type,  and  of  that  type  only  the 
lowest  class,  and,  indeed,  if  we  push  the  theory 
to  its  logical  consequences,  only  the  lowest  forms 
of  the  lowest  class.  What  are  now  the  facts? 
This  continent  affords  admirable  opportunities  for 


GRADATION  AMONG  ANIMALS.  93 

the  investigation  of  this  succession,  because,  in 
consequence  of  its  mode  of  formation,  we  have, 
in  the  State  of  New  York,  a  direct,  unbroken  se- 
quence of  all  the  earliest  geological  deposits. 

The  ridge  of  low  hills,  called  the  Laurentian 
Hills,  along  the  line  of  division  between  Canada 
and  the  States  was  the  first  American  land  lifted 
above  the  ocean.  That  land  belongs  to  the  Azoic 
period,  and  contains  no  trace  of  life.  Along  the 
base  of  that  range  of  hills  lie  the  deposits  of  the 
next  great  geological  period,  the  Silurian ;  and 
the  State  of  New  York,  geologically  speaking, 
belongs  almost  entirely  to  this  Silurian  period, 
with  its  lowest  Taconic  division,  and  the  Devon- 
ian period,  the  third  in  succession  of  these  great 
epochs.  I  need  hardly  remind  those  of  my  read- 
ers who  have  travelled  through  New  York,  and 
have  visited  Niagara  or  Trenton,  or,  indeed,  any 
of  the  localities  where  the  broken  edges  of  the 
strata  expose  the  buried  life  within  them,  how 
numerous  this  early  population  of  the  earth  must 
have  been.  No  one  who  has  held  in  his  hand  one 
of  the  crowded  slabs  of  sandstone  or  limestone, 
or  slate  full  of  Crustacea,  Shells,  and  Corals, 
from  any  of  the  old  Silurian  or  Devonian  beaches 
which  follow  each  other  from  north  to  south 
across  the  State  of  New  York,  can  suppose  that 
the  manifestation  of  life  was  less  multitudinous 
then  than  now. 


94  GRADATION  AMONG  ANIMALS. 

Now,  what  does  this  fossil  creation  tell  us  ?  It 
says  this :  that,  in  the  Silurian  period,  taken  in 
its  most  comprehensive  sense,  the  first  in  which 
organic  life  is  found  at  all,  there  were  the  three 
classes  of  Radiates,  the  three  classes  of  Mollusks, 
two  of  the  classes  of  Articulates,  and  one  class  of 
Vertebrates.  In  other  words,  at  the  dawn  of  life 
on  earth,  the  plan  of  the  animal  creation  with  its 
four  fundamental  ideas  was  laid  out,  —  Radiates, 
Mollusks,  Articulates,  and  Yertebrates  were  pres- 
ent at  that  first  representation  of  life  upon  our 
globe.  If,  then,  all  the  primary  types  appeared 
simultaneously,  one  cannot  have  grown  out  of 
another,  —  they  could  not  be  at  once  contempo- 
raries and  descendants  of  each  other. 

The  diagram  on  the  opposite  page  represents 
the  geological  periods  in  their  regular  succession, 
and  the  approximate  time  at  which  all  the  types 
and  all  the  classes  of  the  Animal  Kingdom  were 
introduced  ;  for  there  is  still  some  doubt  as  to  the 
exact  period  of  the  introduction  of  several  of  the 
classes,  though  all  geologists  are  agreed  respect- 
ing them,  within  certain  limits,  not  very  remote 
from  each  other,  according  to  geological  esti- 
mates of  time. 

If  such  discussions  were  not  inappropriate  here 
from  their  technical  character,  I  think  I  could 
show,  upon  combined  geological  and  zoological 
evidence,  that  the  classes  which  are  not  present 


GRADATION  AMONG  ANIMALS. 


95 


PRIMARY. 


SECONDARY. 


f  I 


hino- 
rms. 


96  GEADATION  AMONG  ANIMALS. 

with  the  others  at  the  beginning,  such  as  Insects 
among  Articulates,  or  Reptiles,  Birds,  and  Mam- 
malia among  Vertebrates,  are  always  introduced 
at  the  time  when  the  conditions  essential  to  their 
existence  are  established,  —  as,  for  instance,  Rep- 
tiles, at  the  period  when  the  earth  was  not  fully 
redeemed  from  the  waste  of  waters,  and  exten- 
sive marshes  afforded  means  for  the  half-aquatic, 
half-terrestrial  life  even  now  characteristic  of  all 
our  larger  Reptiles,  while  Insects,  so  dependent 
on  vegetable  growth,  make  their  appearance  with 
the  first  forests ;  so  that  we  need  not  infer,  be- 
cause these  and  other  classes  come  in  after  the 
earlier  ones,  that  they  are  therefore  a  growth  out 
of  them,  since  it  is  altogether  probable  that  they 
would  not  be  created  till  the  conditions  necessary 
for  their  maintenance  on  earth  were  established. 
From  a  merely  speculative  point  of  view  it 
seems  to  me  natural  to  suppose  that  the  physical 
and  the  organic  world  have  progressed  together, 
and  that  there  is  a  direct  relation  between  the 
successive  creations  and  the  condition  of  the 
earth  at  the  time  of  those  creations.  We  know 
that  all  the  beings  of  the  Silurian  and  Devonian 
periods  were  marine  ;  the  land,  so  far  as  it  existed 
in  their  time,  consisted  of  great  beaches,  and  along 
those  shores,  wherever  any  part  of  the  continent 
was  lifted  above  the  level  of  the  waters,  the  Silu- 
rian and  Devonian  animals  lived.  Later  in  the 


GRADATION  AMONG  ANIMALS.  97 

marshes  and  the  fern-forests  of  the  Carboniferous 
period,  Reptiles  and  Insects  found  their  place ; 
and  only  when  the  earth  was  more  extensive, 
when  marshes  had  become  dry  land,  when  islands 
had  united  to  form  continents,  when  mountain- 
chains  had  been  thrown  up  to  make  the  inequali- 
ties of  the  surface,  were  the  larger  quadrupeds 
introduced,  to  whose  mode  of  existence  all  these 
circumstances  are  important  accessories. 

But  while  all  the  types  and  most  of  the  classes 
were  introduced  upon  the  earth  simultaneously 
at  the  beginning,  these  types  and  classes  have 
nevertheless  been  represented  in  every  great  geo- 
logical period  by  different  sets  or  species  of  ani- 
mals. In  this  sense,  then,  there  has  been  a  gra- 
dation in  time  among  animals,  and  every  succes- 
sive epoch  of  the  world's  physical  history  has  had 
its  characteristic  population.  We  have  found 
that  there  is  a  correspondence  between  the  grada- 
tion of  structural  complication  among  adult  ani- 
mals as  known  to  us  to-day,  which  we  may  call 
the  Series  of  Rank,  and  the  gradation  of  embry- 
ological  changes  in  the  same  animals,  which  we 
may  call  the  Series  of  Growth ;  and  there  is 
also  a  correspondence  between  these  two  series 
and  the  order  of  succession  in  time,  that  estab- 
lishes a  certain  gradation  in  the  introduction  of 
animals  upon  earth,  and  which  we  may  call  the 
Series  of  Time. 


98  GRADATION  AMONG    ANIMALS. 

Take  as  an  illustration  the  class  of  Echino- 
derms.  The  first  representatives  of  this  class 
were  a  sort  of  Star-Fishes  on  stems ;  then  were 
introduced  animals  of  the  same  order  without 
stems ;  in  later  periods  come  in  the  true  Star- 
Fishes  and  Sea-Urchins ;  and  the  highest  order 
of  the  class,  the  Holothurians,  are  introduced 
only  in  the  present  geological  epoch.  Compare 
now  with  this  the  ordinal  division  of  the  class  as 
it  exists  to-day.  The  present  representative  of 
those  earliest  Echinoderms  on  stems  is  an  animal 
that  upon  structural  evidence  stands  lowest  in 
the  class ;  next  above  it  are  the  Comatulee,  cor- 
responding to  the  early  Echinoderms  without 
stems ;  next  in  our  classification  are  the  Star- 
Fishes  and  Sea-Urchins ;  and  the  Holothurians 
stand  highest,  on  account  of  certain  structural 
features  that  place  them  at  the  head  of  their 
class.  The  Series  of  Time  and  the  Series  of 
Rank,  then,  accord  perfectly,  and  investiga- 
tions of  the  embryological  development  of  these 
animals  have  shown  that  the  higher  Echinoderms 
pass  through  changes,  during  their  growth,  that 
indicate  the  same  kind  of  gradation,  for  the  young 
in  some  of  them  have  a  stem  which  is  gradually 
dropped,  and  their  successive  phases  of  develop- 
ment recall  the  adult  forms  of  the  lower  orders. 

Take  as  another  illustration  the  class  of  Pol- 
yps. First  in  time  among  the  early  Reef-Build- 


GRADATION  AMONG  ANIMALS.  99 

ers,  who  wrought  their  myriad  lives  into  the  solid 
crust  of  our  globe  then,  as  their  successors  do  now, 
we  find  a  peculiar  kind  of  Polyp  Coral.  These 
old  Corals  have  their  representatives  among  the 
present  Polyps,  and  from  their  structure  they 
are  placed  lowest  in  their  class,  while  the  embry- 
ological  development  of  the  higher  ones  recalls 
in  the  younger  condition  of  the  germ  the  same 
character.  I  might  multiply  examples,  and 
draw  equally  striking  illustrations  from  the  other 
classes ;  and  though  these  correspondences  can- 
not be  fully  established  while  our  knowledge  of 
the  embryological  growth  of  animals  is  so  scanty, 
and  there  remain  so  many  gaps  in  our  informa- 
tion about  their  geological  succession,  yet  wher- 
ever we  have  been  able  to  trace  the  connected 
history  of  any  group  of  animals  in  time,  and  to 
compare  it  with  the  history  of  their  embryologi- 
cal development  and  their  structural  relations  as 
they  exist  to-day,  the  correspondence  is  found  to 
be  so  complete  as  to  justify  us  in  the  belief  that 
it  will  not  fail  in  other  instances. 

I  may  add  that  a  gradation  of  exactly  the  same 
character  controls  the  geographical  distribution 
of  animals  over  the  surface  of  the  globe.  Here 
again  I  must  beg  my  readers  to  take  much  of  the 
evidence,  which,  if  expanded,  would  fill  many 
volumes,  for  granted,  since  it  would  be  entirely 
inappropriate  here.  But  I  may  briefly  state  that 


100  GRADATION  AMONG   ANIMALS. 

animals  are  not  scattered  over  the  surface  of  our 
globe  at  random,  but  that  they  are  associated  to- 
gether in  what  are  called  faunce,  and  that  these 
faunas  have  their  homes  within  certain  districts 
called  by  naturalists  zoological  provinces.  The 
limits  of  these  provinces  are  absolutely  fixed,  in 
the  ocean  as  well  as  on  the  land,  by  certain  phys- 
ical conditions  connected  with  climate,  with  alti- 
tude, with  the  pressure  of  the  atmosphere,  the 
weight  of  the  water,  etc. ;  and  this  is  true  even 
for  animals  of  migratory  habits,  for  all  such  mi- 
grations are  periodical,  and  have  boundaries  as 
definite  and  impassable  as  those  that  limit  the  per- 
manent homes  of  animals.  There  is  a  certain 
series  established  by  the  relations  between  differ- 
ent kinds  of  animals,  as  thus  distributed  over  the 
globe,  agreeing  witli  the  gradation  in  their  rank, 
their  growth,  and  their  succession  in  time  ;  —  the 
law  which  distributes  animals  in  adjoining  faunas, 
and  in  accordance  both  with  their  relative  superi- 
ority or  inferiority,  and  with  the  physical  condi- 
tions essential  to  their  existence,  being  the  same 
as  that  which  controls  their  structural  relations, 
their  embryological  development,  and  their  suc- 
cession in  time. 

What,  then,  does  this  correspondence  between 
the  Series  of  Rank,  the  Series  of  Growth,  the 
Series  of  Time,  and  the  Series  of  Geographi- 
cal Distribution  in  the  life  of  animals  teach  us  ? 


GRADATION  AMONG  ANIMALS.;    \  '>',]  101 


Surely  not  that  the  connection  between',  {iniiiipT?; 
is  a  material  one  ;  for  the  same  kind  of  relation 
exists  between  lower  and  higher  animals  of  one 
type  or  one  class  to-day,  in  their  structural  fea- 
tures, in  their  embryological  growth,  and  in  their 
geographical  distribution,  as  we  trace  in  their 
order  of  succession  in  time  ;  and  therefore,  if 
this  kind  of  evidence  proves  that  the  later  ani- 
mals are  the  descendants  of  the  earlier  in  any 
genealogical  sense,  it  should  also  prove  that  the 
animals  living  in  one  part  of  the  earth  at  present 
grow  out  of  animals  living  in  another  part,  and 
that  the  higher  animals  of  one  class  as  it  exists 
now  are  developed  out  of  the  lower  ones.  The 
first  of  these  propositions  needs  no  refutation  ; 
and  with  regard  to  the  second,  all  our  investiga- 
tions go  to  show  that  every  being  born  into  the 
world  to-day  adheres  to  its  individual  law  of  life, 
and  though  it  passes  through  transient  phases  of 
growth  resembling  other  beings  of  its  own  kind, 
never  pauses  at  a  lower  stage  of  development, 
or  passes  on  to  a  higher  condition  than  the  one 
it  is  bound  to  fill. 

If,  then,  this  connection  is  not  a  material  one, 
what  is  it  ?  —  for  that  such  a  connection  does  ex- 
ist throughout  the  Animal  Kingdon,  as  intimate, 
as  continuous,  as  complex,  as  any  series  which  the 
development  theorists  have  ever  contended  for,  is 
not  to  be  denied.  What  can  it  be  but  an  intel- 


;        :  GRADATION   AMONG  ANIMALS. 


?  These  correspondences  are  corre- 
spondences of  thought,  —  of  a  thought  that  is 
always  the  same,  whether  it  is  expressed  in  the 
history  of  the  type  through  all  time,  or  in  the  life 
of  the  individuals  that  represent  the  type  at  the 
present  moment,  or  in  the  growth  of  the  germ  of 
every  being  born  into  that  type  to-day.  In  other 
words,  the  same  thought  that  spans  the  whole 
succession  of  geological  ages  controls  the  struct- 
ural relations  of  all  living  beings  as  well  as  their 
distribution  over  the  surface  of  the  earth,  and  is 
repeated  within  the  narrow  compass  of  the  small- 
est egg  in  which  any  being  begins  its  growth. 


ANALOGOUS   TYPES.  103 


CHAPTER  VII. 

ANALOGOUS  TYPES. 

I  COME  now  to  an  obscure  part  of  my  subject, 
very  difficult  to  present  in  a  popular  form,  and 
yet  so  important  in  the  scientific  investigations 
of  our  day  that  I  cannot  omit  it  entirely.  I  al- 
lude to  what  are  called  by  naturalists  Collateral 
Series  or  Parallel  and  Analogous  Types.  These 
are  by  no  means  difficult  to  trace,  because  they 
are  connected  by  seeming  resemblances,  which, 
though  very  likely  to  mislead  and  perplex  the 
observer,  yet  naturally  suggest  the  association 
of  such  groups.  Let  me  introduce  the  subject 
with  the  statement  of  some  facts. 

There  are  in  Australia  numerous  Mammalia, 
occupying  the  same  relation  and  answering  the 
same  purposes  as  the  Mammalia  of  other  coun- 
tries. Some  of  them  are  domesticated  by  the  na- 
tives, and  serve  them  with  meat,  milk,  and  wool, 
as  our  domesticated  animals  serve  us.  Repre- 
sentatives of  almost  all  types,  Wolves,  Foxes, 
Sloths,  Bears,  Weasels,  Martens,  Squirrels,  Rats, 
etc.,  are  found  there ;  and  yet,  though  all  these 


104  ANALOGOUS   TYPES. 

animals  resemble  ours  so  closely  that  the  Eng- 
lish settlers  have  called  many  of  them  by  the 
same  names,  there  are  no  genuine  Wolves,  Foxes, 
Sloths,  Bears,  Weasels,  Martens,  Squirrels,  or 
Rats  in  Australia.  The  Australian  Mammalia 
are  peculiar  to  the  region  where  they  are  found, 
and  are  all  linked  together  by  two  remarkable 
structural  features  which  distinguish  them  from 
all  other  Mammalia  and  unite  them  under  one 
head  as  the  so-called  Marsupials.  They  bring 
forth  their  young  in  an  imperfect  condition,  and 
transfer  them  to  a  pouch,  where  they  remain 
attached  to  the  teats  of  the  mother  till  their 
development  is  as  far  advanced  as  that  of  other 
Mammalia  at  the  time  of  their  birth  ;  and  they 
are  further  characterized  by  an  absence  of  that 
combination  of  transverse  fibres  forming  the  large 
bridge  which  unites  the  two  hemispheres  of  the 
brain  in  all  the  other  members  of  their  class. 
Here,  then,  is  a  series  of  animals  parallel  with 
ours,  separated  from  them  by  anatomical  fea- 
tures, but  so  united- with  them  by  form  and  ex- 
ternal features  that  many  among  them  have  been 
at  first  associated  together. 

Cuvier  has  already  alluded  to  this,  when  he 
speaks  of  subordination  of  characters,  distinguish- 
ing between  those  controlling  the  whole  organ- 
ization and  those  that  play  only  a  secondary 
part  in  it.  The  skill  of  the  naturalist  consists 


ANALOGOUS   TYPES.  105 

in  detecting  the  difference  between  the  two,  so 
that  he  may  not  take  the  more  superficial  features 
as  the  basis  of  his  classification,  instead  of  those 
important  ones  which,  though  often  less  easily 
recognized,  are  more  deeply  rooted  in  the  organ- 
ization. It  is  a  difference  of  the  same  nature 
as  that  between  affinity  and  analogy,  to  which  I 
have  alluded  before,  when  speaking  of  the  in- 
grafting of  certain  features  of  one  type  upon  ani- 
mals of  another  type,  thus  producing  a  superficial 
resemblance,  not  truly  characteristic.  In  the 
Reptiles,  for  instance,  there  are  two  groups, — 
those  devoid  of  scales,  with  naked, skin,  laying 
numerous  eggs,  but  hatching  their  young  in  an 
imperfect  state,  and  the  Scaly  Reptiles,  which  lay 
comparatively  few  eggs,  but  whose  young,  when 
hatched,  are  completely  developed,  and  undergo 
no  subsequent  metamorphosjs.  Yet,  notwith- 
standing this  difference  in  essential  features  of 
structure,  and  in  the  mode  of  reproduction  and 
development,  there  is  such  an  external  resem- 
blance between  certain  animals  belonging  to  the 
two  groups  that  they  were  associated  together 
even  by  so  eminent  a  naturalist  as  Linna3us. 
Compare,  for  example,  the  Serpents  among  the 
Scaly  Reptiles  with  the  Csecilians  among  the 
Naked  Reptiles.  They  have  the  same  elongated 
form,  and  are  both  destitute  of  limbs  ;  the  head 
in  both  is  on  a  level  with  the  body,  without  any 

5* 


106  ANALOGOUS   TYPES. 

contraction  behind  it,  such  as  marks  the  neck  in 
the  higher  Reptiles,  and  moves  only  by  the  action 
of  the  backbone ;  they  are  singularly  alike  in 
their  external  features,  but  the  young  of  the  Ser- 
pent are  hatched  in  a  mature  condition,  while 
the  young  of  the  type  to  which  the  Cascilians 
belong  undergo  a  succession  of  metamorphoses 
before  their  resemblance  to  the  parent  is  clearly 
denned.  Or  compare  the  Lizard  and  the  Sala- 
mander, in  which  the  likeness  is  perhaps  even 
more  striking;  for  any  inexperienced  observer 
would  mistake  one  for  the  other.  Both  are  in 
some  respects  superior  to  the  Serpents  and  Ca3- 
cilians,  for  in  them  the  head  moves  freely  on  the 
neck,  and  they  creep  on  short,  imperfect  legs. 
But  the  Lizard  is  clothed  with  scales,  while 
the  body  of  the  Salamander  is  naked,  and  the 
young  of  the  former  is  complete  when  hatched, 
while  the  Tadpole  born  from  the  Salamander  has 
a  life  of  its  own  to  live,  with  certain  changes  to 
pass  through  before  it  assumes  its  mature  con- 
dition ;  during  the  early  part  of  its  life  it  is  even 
destitute  of  legs,  and  has  gills  like  the  Fishes. 

Above  the  Lizards  and  Salamanders,  highest 
in  the  class  of  Reptiles,  stand  two  other  collat- 
eral types,  —  the  Turtles  at  the  head  of  the  Scaly 
Reptiles,  the  Toads  and  Frogs  at  the  head  of  the 
Naked  Reptiles.  The  external  likeness  between 
these  two  groups  is  perhaps  less  striking  than 


ANALOGOUS   TYPES.  107 

between  those  mentioned  above,  on  account  of 
the  large  shield  of  the  Turtle.  But  there  are 
Turtles  with  a  soft  covering,  and  there  are  some 
Toads  with  a  hard  shield  over  the  head  and  neck 
at  least,  and  both  groups  are  alike  distinguished 
by  the  shortness  and  breadth  of  the  body  and 
by  the  greater  development  of  the  limbs  as  com- 
pared with  the  lower  Reptiles.  But  here  again 
there  is  the  same  essential  difference  in  the  mode 
of  development  of  their  young  as  distinguishes 
all  the  rest.  The  two  series  may  thus  be  con- 
trasted :  — 

Naked  Reptiles.  Scaly  Reptiles. 
Toads  and  Frogs,  Turtles, 

Salamanders,  Lizards, 

Caecilians.  Serpents. 

Such  corresponding  groups  or  parallel  types, 
united  only  by  external  resemblance,  and  dis- 
tinguished from  each  other  by  essential  elements 
of  structure,  exist  among  all  animals,  though 
they  are  less  striking  among  Birds  on  account 
of  the  uniformity  of  that  class.  Yet  even  there 
we  may  trace  such  analogies,  —  as  between  the 
Palmate  or  Aquatic  Birds,  for  instance,  and  the 
Birds  of  Prey,  or  between  the  Frigate  Bird  and 
the  Kites.  Among  Fishes  such  analogies  are 
very  common,  often  suggesting  a  comparison 
even  with  land  animals,  though  on  account  of 
the  scales  and  spines  of  the  former  the  likeness 


108  ANALOGOUS   TYPES. 

may  not  be  easily  traced.  But  the  common 
names  used  by  the  fishermen  often  indicate  these 
resemblances,  —  as,  for  instance,  Sea-Yulture, 
Sea-Eagle,  Cat-Fish,  Flying-Fish,  Sea-Porcupine, 
Sea-Cow,  Sea-Horse,  and  the  like. 

In  the  branch  of  Mollusks,  also,  the  same 
superficial  analogies  are  found.  In  the  lowest 
class  of  this  division  of  the  Animal  Kingdom 
there  is  a  group  so  similar  to  the  Polyps,  that, 
until  recently,  they  have  been  associated  with 
them,  —  the  Bryozoa.  They  are  very  small  ani- 
mals, truly  allied  to  the  Clams  by  the  plan  of 
their  structure,  but  resembling  the  Polyps  on 
account  of  a  radiating  wreath  of  feelers  around 
the  upper  part  of  their  body:  yet,  when  exam- 
ined closely,  this  wreath  is  found  to  be  incom- 
plete ;  it  does  not  form  a  circle,  but  leaves  an 
open  space  between  the  two  ends,  where  they 
approach  each  other,  so  that  it  has  a  horseshoe 
outline,  and  partakes  of  the  bilateral  symmetry 
characteristic  of  its  type  and  on  which  its  own 
structure  is  based.  These  series  have  not  yet 
been  very  carefully  traced,  and  young  natural- 
ists should  turn  their  attention  to  them,  and  be 
prepared  to  draw  the  nicest  distinction  between 
analogies  and  true  affinities  among  animals. 


FAMILY   CHARACTERISTICS.  10 rJ 


CHAPTER    VIII. 

FAMILY   CHARACTERISTICS. 

LET  us  proceed  to  a  careful  examination  of 
the  natural  groups  of  animals  called  Families 
by  naturalists,  —  a  subject  already  briefly  alluded 
to  in  a  previous  chapter.  Families  are  natu- 
ral assemblages  of  animals  less  extensive  than 
Orders,  but,  like  Orders,  Classes,  and  Branches, 
founded  upon  certain  categories  of  structure, 
as  distinct  for .  this  kind  of  group  as  are  those 
above  specified  for  the  other  divisions  in  the 
classification  of  the  Animal  Kingdom,  which  we 
have  thus  far  examined. 

That  we  may  understand  the  true  meaning 
of  these  divisions,  we  must  not  be  misled  by  the 
name  given  by  naturalists  to  this  kind  of  groups. 
Here,  as  in  so  many  other  instances,  a  word 
already  familiar,  and  as  it  were  identified  with 
the  special  sense  in  which  it  had  been  used, 
was  adopted  by  science,  and  received  a  new  sig- 
nification. When  naturalists  speak  of  Families 
among  animals,  they  do  not  allude  to  the  proge- 
ny of  a  known  stock,  as  we  designate,  in  com- 


110  FAMILY   CHARACTEEISTICS. 

mon  parlance,  the  children  or  the  descendants 
of  known  parents  ;  they  understand  by  this  name 
natural  groups  including  different  kinds  of  ani- 
mals, having  no  genetic  relations  so  far  as  we 
know,  but  agreeing  with  one  another  closely 
enough  to  leave  the  impression  of  a  more  or 
less  remote  common  parentage.  The  difficulty 
here  consists  in  determining  the  natural  limits 
of  such  groups,  and  in  tracing  the  characteristic 
features  by  which  they  may  be  defined ;  for  in- 
dividual investigators  differ  greatly  as  to  the  de- 
gree of  resemblance  existing  between  the  mem- 
bers of  many  Families,  and  there  is  no  kind  of 
group  which  presents  greater  diversity  of  circum- 
scription in  the  classifications  of  animals  pro- 
posed by  different  naturalists  than  these  so-called 
Families. 

It  should  be  remembered,  however,  that,  unless 
a  sound  criterion  be  applied  to  the  limitation  of 
Families,  they,  like  all  other  groups  introduced 
into  zoological  systems,  must  forever  remain  arbi- 
trary divisions,  as  they  have  been  hitherto.  A 
retrospective  glance  at  the  progress  of  our  sci- 
ence during  the  past  century,  in  this  connection, 
may  perhaps  help  us  to  solve  the  difficulty. 
Linnaeus,  in  his  System  of  Nature,  does  not  ad- 
mit Families ;  he  has  only  four  kinds  of  groups, 
—  Classes,  Orders,  Genera,  and  Species.  It  was, 
as  I  have  stated  in  a  previous  chapter,  among 


FAMILY   CHARACTERISTICS.  Ill 

plants  that  naturalists  first  perceived  those  gen- 
eral traits  of  resemblance  existing  everywhere 
among  the  members  of  natural  families,  in  con- 
sequence of  which  they  added  this  kind  of  group 
to  the  framework  of  their  system.  In  France, 
particularly,  this  method  was  pursued  with  suc- 
cess ;  and  the  improvements  thus  introduced  by 
the  French  botanists  were  so  great,  and  rendered 
their  classification  so  superior  to  that  of  Linnae- 
us, that  the  botanical  systems  in  which  Families 
were  introduced  were  called  natural  systems,  in 
contradistinction  especially  to  the  botanical  clas- 
sification of  Linnaeus,  which  was  founded  upon 
the  organs  of  reproduction,  and  which  received 
thenceforth  the  name  of  the  sexual  system  of 
plants.  The  same  method  so  successfully  used 
by  botanists  was  soon  introduced  into  Zoology 
by  the  French  naturalists  of  the  beginning  of 
this  century,  —  Lamarck,  Latreille,  and  Cuvier. 
But,  to  this  day,  the  limitation  of  Families  among 
animals  has  not  reached  the  precision  which  it 
has  among  plants,  and  I  see  no  other  reason  for 
the  difference  than  the  absence  of  a  leading  prin- 
ciple to  guide  us  in  Zoology. 

Families,  as  they  exist  in  Nature,  are  based  up- 
on peculiarities  of  form  as  dependent  upon  struc- 
ture ;  but  though  a  very  large  number  of  them 
have  been  named  and  recorded,  very  few  are  char- 
acterized with  anything  like  scientific  accuracy. 


112  FAMILY   CHARACTERISTICS. 

It  has  been  a  very  simple  matter  to  establish  such 
groups  according  to  the  superficial  method  that 
has  been  pursued,  for  the  fact  that  they  are  de- 
termined by  external  outline  renders  the  recogni- 
tion of  them  easy  and  in  many  instances  almost 
instinctive  ;  but  it  is  very  difficult  to  characterize 
them,  or,  in  other  words,  to  trace  the  connection 
between  form  and  structure.  Indeed,  many 
naturalists  do  not  admit  that  Families  are  based 
upon  form ;  and  it  was  in  trying  to  account  for 
the  facility  with  which  they  detect  these  groups, 
while  they  find  it  so  difficult  to  characterize 
them,  that  I  perceived  them  to  be  always  associat- 
ed with  peculiarities  of  form.  Naturalists  have 
established  Families  simply  by  bringing  together 
a  number  of  animals  resembling  each  other  more 
or  less  closely,  and,  taking  usually  the  name  of 
the  Genus  to  which  the  best  known  among  them 
belongs,  they  have  given  it  a  patronymic  termi- 
nation to  designate  the  Family,  and  allowed  the 
matter  to  rest  there,,  sometimes  without  even  at- 
tempting any  description  corresponding  to  those 
by  which  Genus  and  Species  are  commonly  de- 
fined. 

For  instance,  from  Canis,  the  Bog,  Canidce  has 
been  formed,  to  designate  the  whole  Family  of 
Dogs,  Wolves,  Foxes,  etc.  Nothing  can  be  more 
superficial  than  such  a  mode  of  classification ; 
and  if  these  groups  actually  exist  in  Nature,  they 


FAMILY   CHAKACTERISTICS.  113 

must  be  based,  like  all  the  other  divisions,  upon 
some  combination  of  structural  characters  pecu- 
liar to  them.  We  have  seen  that  Branches  are 
founded  upon  the  general  plan  of  structure, 
Classes  upon  the  execution  of  the  plan,  Orders 
upon  the  greater  or  less  complication  of  a  given 
mode  of  execution,  and  we  shall  find  that  form, 
as  determined  by  structure,  characterizes  Fami- 
lies. I  would  call  attention  to  this  qualification 
of  my  definition  ;  since,  of  course,  when  speak- 
ing of  form  in  this  connection,  I  do  not  mean  those 
superficial  resemblances  in  external  features  al- 
ready alluded  to  in  my  remarks  upon  Parallel  or 
Collateral  Types.  I  speak  now  of  form  as  con- 
trolled by  structural  elements ;  and  unless  we 
analyze  Families  in  this  way,  the  mere  distin- 
guishing and  naming  them  does  not  advance  our 
science  at  all. 

Compare,  for  instance,  the  Dogs,  the  Seals, 
and  the  Bears.  These  are  all  members  of  one 
order,  —  that  of  the  Carnivorous  Mammalia. 
Their  dentition  is  peculiar  and  alike  in  all  (cut- 
ting teeth,  canine  teeth,  and  grinders),  adapted 
for  tearing  and  chewing  their  food  ;  and.  their  in- 
ternal structure  bears  a  definite  relation  to  their 
dentition.  But  look  at  these  animals  with  refer- 
ence to  form.  The  Dog  is  comparatively  slender, 
with  legs  adapted  for  running  and  hunting  his 
prey ;  the  Bear  is  heavier,  with  shorter  limbs ; 


114  FAMILY   CHARACTERISTICS. 

while  the  Seal  has  a  continuous  uniform  outline 
adapted  for  swimming.  They  form  separate 
Families,  and  are  easily  recognized  as  such  by  the 
difference  in  their  external  outline ;  but  what  is 
the  anatomical  difference  producing  the  peculiar- 
ity of  form  in  each,  by  which  they  have  been 
thus  distinguished  ?  It  lies  in  the  structure  of 
the  limbs,  and  especially  in  that  of  the  wrist 
and  fingers.  In  the  Seal  the  limbs  are  short,  and 
the  wrists  are  on  one  continuous  line  with  them, 
so  that  it  has  no  power  of  bending  the  wrist  or 
the  fingers,  and  the  limbs,  therefore,  act  like  flap- 
pers or  oars.  The  Bear  has  a  well-developed  paw 
with  a  flexible  wrist,  but  it  steps  on  the  whole 
sole  of  the  foot,  from  the  wrist  to  the  tip  of  the 
toe,  giving  it  the  heavy  tread  so  characteristic  of 
all  the  Bears.  The  Dogs,  on  the  contrary,  walk 
on  tiptoe,  and  their  step,  though  firm,  is  light, 
while  the  greater  slenderness  and  flexibility  of 
their  legs  add  to  their  nimbleness  and  swiftness. 
By  a  more  extensive  investigation  of  the  anatom- 
ical structure  of  the  limbs  in  their  connection 
with  the  whole  body,  it  could  easily  be  shown 
that  the  peculiarity  of  form  in  these  animals  is 
essentially  determined  by,  or  at  least  stands  in 
the  closest  relation  to,  the  peculiar  structure  of 
the  wrist  and  fingers. 

Take  the   Family   of  Owls,   as   distinguished 
from  the  Falcons,  Kites,  etc.     Here  the  differ- 


FAMILY   CHAKACTERISTICS.  115 

ence  of  form  consists  in  the  position  of  the  eyes. 
In  the  Owl,  the  sides  of  the  head  are  prominent, 
and  the  eye-socket  is  brought  forward.  In  the 
Falcons  and  Kites,  on  the  contrary,  the  sides  of 
the  head  are  flattened,  and  the  eyes  are  set  back. 
The  difference  in  the  appearance  of  the  birds  is 
evident  to  the  most  superficial  observer ;  but  to 
call  the  one  Strigidse  and  the  other  Falconidse 
tells  us  nothing  of  the  anatomical  peculiarities 
on  which  this  difference  is  founded. 

These  few  examples,  selected  purposely  among 
closely  allied  and  universally  known  animals, 
may  be  sufficient  to  show,  that,  beyond  the  general 
complication  of  the  structure  which  character- 
izes the  Orders,  there  is  a  more  limited  element 
in  the  organization  of  animals,  bearing  chiefly 
upon  their  form,  which,  if  it  have  any  general 
application  as  a  principle  of  classification,  may 
well  be  considered  as  essentially  characteristic  of 
the  Families.  There  are  certainly  closely  allied 
natural  groups  of  animals,  belonging  to  the  same 
Order,  but  including  many  Genera,  which  differ 
from  each  other  chiefly  in  their  form,  while  that 
form  is  determined  by  peculiarities  of  structure 
which  do  not  influence  the  general  structural 
complication  upon  which  Orders  are  based,  or  re- 
late to  the  minor  details  of  structure  on  which 
Genera  are  founded.  I  am,  therefore,  convinced 
that  form  is  the  criterion  by  which  Families  may 


116  FAMILY  CHARACTERISTICS. 

be  determined.  The  great  facility  with  which 
animals  may  be  combined  together  in  natural 
groups  of  this  kind  without  any  special  investi- 
gation of  their  structure  —  a  superficial  method 
of  classification  in  which  zoologists  have  lately 
indulged  to  a  most  unjustifiable  degree  —  con- 
vinces me  that  it  is  the  similarity  of  form  which 
has  unconsciously  led  such  shallow  investigators 
to  correct  results,  since  upon  close  examination 
it  is  found  that  a  large  number  of  the  Families 
so  determined,  and  to  which  no  characters  at  all 
are  assigned,  nevertheless  bear  the  severest  criti- 
cism founded  upon  anatomical  investigation. 

The  questions  proposed  to  themselves  by  all 
students  who  would  characterize  Families  should 
be  these :  What  are,  throughout  the  Animal 
Kingdom,  the  peculiar  patterns  of  form  by  which 
Families  are  distinguished  ?  and  on  what  struct- 
ural features  are  these  patterns  based  ?  Only  the 
most  patient  investigations  can  give  us  the  an- 
swer, and  it  will  be  very  long  before  we  can  write 
out  the  formulae  of  these  patterns  with  mathe- 
matical precision,  as  I  believe  we  shall  be  able  to 
do  in  a  more  advanced  stage  of  our  science. 
But  while  the  work  is  in  progress,  it  ought  to  be 
remembered  that  a  mere  general  similarity  of 
outline  is  not  yet  in  itself  evidence  of  identity  of 
form  or  pattern,  and  that,  while  seemingly  very 
different  forms  may  be  derived  from  the  same 


FAMILY   CHARACTERISTICS.  117 

formula,  the  most  similar  forms  may  belong  to 
entirely  different  systems,  when  their  derivation 
is  properly  traced. 

Our  great  mathematician,  in  a  lecture  delivered 
at  the  Lowell  Institute  last  winter,  showed  that 
in  his  science,  also,  similarity  of  outline  does  not 
always  indicate  identity  of  character.  Compare 
the  different  circles,  —  the  perfect  circle,  in  which 
every  point  of  the  periphery  is  at  the  same  dis- 
tance from  the  centre,  with  an  ellipse  in  which  the 
variation  from  the  true  circle  is  so  slight  as  to  be 
almost  imperceptible  to  the  eye  ;  yet  the  latter,  like 
all  ellipses,  has  its  two  foci  by  which  it  differs  from 
a  circle,  and  to  refer  it  to  the  family  of  circles 
instead  of  the  family  of  ellipses  would  be  overlook- 
ing its  true  character  on  account  of  its  external 
appearance  ;  and  yet  ellipses  may  be  so  elongated, 
that,  far  from  resembling  a  circle,  they  make  the 
impression  of  parallel  lines  linked  at  their  ex- 
tremities. Or  we  may  have  an  elastic  curve  in 
which  the  appearence  of  a  circle  is  produced  by 
the  meeting  of  the  two  ends  ;  nevertheless  it 
belongs  to  the  family  of  elastic  curves,  in  which 
may  even  be  included  a  line  actually  straight,  and 
is  formed  by  a  process  entirely  different  from  that 
which  produces  the  circle  or  the  ellipse. 

But  it  is  sometimes  exceedingly  difficult  to 
find  the  relation  between  structure  and  form  in 
Families.  I  remember  a  case  which  I  had  taken 


118  FAMILY   CHARACTERISTICS. 

as  a  test  of  the  accuracy  of  the  views  I  enter- 
tained upon  this  subject,  and  which  perplexed 
and  baffled  me  for  years.  It  was  that  of  our 
fresh-water  Mussels,  the  Family  of  Unios.  There 
is  a  great  variety  of  outline  among  them,  —  some 
being  oblong  and  very  slender,  others  broad  with 
seemingly  square  outlines,  others  having  a  nearly 
triangular  form,  while  others  again  are  almost 
circular ;  and  I  could  not  detect  among  them  all 
any  feature  of  form  that  was  connected  with  any 
essential  element  of  their  structure.  At  last, 
however,  I  found  this  test-character,  and  since 
that  time  I  have  had  no  doubt  left  in  my  mind 
that  form,  determined  by  structure,  is  the  true 
criterion  of  Families.  In  the  Unios  it  consists 
of  the  rounded  outline  of  the  anterior  end  of  the 
body  reflected  in  a  more  or  less  open  curve  of 
the  shell,  bending  more  abruptly  along  the  lower 
side  with  an  Inflection  followed  by  a  bulging. 
This  bulging  corresponds  to  the  most  prominent 
part  of  the  gills,  to  which,  in  a  large  number  of 
American  Species  of  this  Family,  the  eggs  are  ex- 
clusively transferred,  giving  to  this  part  of  the 
shell  a  prominence  which  it  has  not  in  any  of  the 
European  Species.  At  the  posterior  end  of  the 
body  this  curve  then  bends  upwards  and  back- 
wards again,  the  outline  meeting  the  side  occu- 
pied by  the  lunge  and  ligament,  which,  when 
very  short,  may  determine  a  triangular  form  of 


FAMILY   CHARACTERISTICS.  119 

the  whole  shell,  or,  when  equal  to  the  lower  side 
and  connected  with  a  great  height  of  the  body, 
gives  it  a  quadrangular  form,  or,  if  the  height  is 
reduced,  produces  an  elongated  form,  or,  finally, 
a  rounded  form,  if  the  passage  from  one  side  to 
the  other  is  gradual.  A  comparison  of  the  po- 
sition of  the  internal  organs  of  different  Species 
of  Unios  with  the  outlines  of  their  shells  will 
leave  no  doubt  that  their  form  is  determined  by 
the  structure  of  the  animal. 

A  few  other  and  more  familiar  examples  may 
complete  these  remarks.  Among  Climbing  Birds, 
for  instance,  which  are  held  together  as  a  more 
comprehensive  group  by  the  structure  of  their 
feet  and  by  other  anatomical  features,  there  are 
two  Families  so  widely  different  in  their  form 
that  they  may  well  serve  as  examples  of  this 
principle.  The  Woodpeckers  (PicidcB)  and  the 
Parrots  (Psittacidce) ,  once  considered  as  two 
Genera  only,  have  both  been  subdivided,  in  con- 
sequence of  a  more  intimate  knowledge  of  their 
generic  characters,  into  a  large  number  of  Gen- 
era ;  but  all  the  Genera  of  Woodpeckers  and  all 
the  Genera  of  the  Parrots  are  still  held  •  together 
by  their  form  as  Families,  corresponding  as  such 
to  the  two  old  Genera  of  Picus  and  Psittacus. 
They  are  now  known  as  the  Families  of  Wood- 
peckers and  Parrots  ;  and  though  each  group  in- 
cludes a  number  of  Genera  combined  upon  a 


120  FAMILY   CHAKACTERISTICS. 

variety  of  details  in  the  finish  of  special  parts  of 
the  structure,  such  as  the  number  of  toes,  the  pe- 
culiarities of  the  bill,  etc.,  it  is  impossible  to  over- 
look the  peculiar  form  characteristic  of  each.  No 
one  who  is  familiar  with  the  outline  of  the  Par- 
rot will  fail  to  recognize  any  member  of  that 
Family  by  a  general  form  which  is  equally  com- 
mon to  the  diminutive  Nonpareil,  the  gorgeous 
Ara,  and  the  high-crested  Cockatoo.  Neither 
will  any  one,  who  has  ever  observed  the  small 
head,  the  straight  bill,  the  flat  back,  and  stiff  tail 
of  the  Woodpecker,  hesitate  to  identify  the  fam- 
ily form  in  any  of  the  numerous  Genera  into 
which  this  group  is  now  divided.  The  family  char- 
acters are  even  more  invariable  than  the  generic 
ones ;  for  there  are  Woodpeckers  which,  instead 
of  the  four  toes,  two  turning  forward  and  two 
backward,  which  form  an  essential  generic  char- 
acter, have  three  toes  only,  while  the  family  form 
is  always  maintained,  whatever  variations  there 
may  be  in  the  characters  of  the  more  limited 
groups  it  includes. 

The  Turtles  and  Terrapins  form  another  good 
illustration  of  family  characters.  They  consti- 
tute together  a  natural  Order,  but  are  distin- 
guished from  each  other  as  two  Families  very 
distinct  in  general  form  and  outline.  Among 
Fishes  I  may  mention  the  Family  of  Pickerels, 
with  their  flat,  long  snout,  and  slender,  almost 


FAMILY   CHARACTEEISTICS.  121 

cylindrical  body,  as  contrasted  with  the  plump, 
compressed  body  and  tapering  tail  of  the  Trout 
Family.  Or  compare,  among  Insects,  the  Hawk- 
Moths  with  the  Diurnal  Butterfly,  or  with  the  so- 
called  Miller,  —  or,  among  Crustacea,  the  com- 
mon Crab  with  the  Sea-Spider,  or  the  Lobsters 
with  the  Shrimps,  —  or,  among  Worms,  the 
Leeches  with  the  Earth- Worms,  —  or,  among 
Mollusks,  the  Squids  with  the  Cuttle-Fishes,  or 
the  Snails  with  the  Slugs,  or  the  Periwinkles 
with  the  Limpets  and  Conchs,  or  the  Clam  with 
the  so-called  Yenus,  or  the  Oyster  with  the  Mother- 
of-Pearl  shell,  —  everywhere,  throughout  the  Ani- 
mal Kingdom,  difference  of  form  points  at  differ- 
ence of  Families. 

There  is  a  chapter  in  the  Natural  History  of 
Animals  that  has  hardly  been  touched  upon  as 
yet,  and  that  will  be  especially  interesting  with 
reference  to  Families.  The  voices  of  animals  have 
a  family  character  not  to  be  mistaken.  All  the 
Canidse  bark  and  howl :  the  Fox,  the  Wolf,  the 
Dog  have  the  same  kind  of  utterance,  though  on 
a  somewhat  different  pitch.  All  the  Bears  growl, 
from  the  White  Bear  of  the  Arctic  snows  to  the 
small  Black  Bear  of  the  Andes.  All  the  Cats 
miau,  from  our  quiet  fireside  companion  to  the 
Lions  and  Tigers  and  Panthers  of  the  forest  and 
jungle.  This  last  may  seem  a  strange  assertion  ; 
but  to  any  one  who  has  listened  critically  to  their 

6 


122  FAMILY   CHARACTERISTICS. 

sounds  and  analyzed  their  voices,  the  roar  of  the 
Lion  is  but  a  gigantic  miau,  bearing  about  the 
same  proportion  to  that  of  a  Cat  as  its  stately 
and  majestic  form  does  to  the  smaller,  softer, 
more  peaceful  aspect  of  the  Cat.  Yet,  notwith- 
standing the  difference  in  their  size,  who  can  look 
at  the  Lion,  whether  in  his  more  sleepy  mood,  as 
he  lies  curled  up  in  the  corner  of  his  cage,  or  in 
his  fiercer  moments  of  hunger  or  of  rage,  with- 
out being  reminded  of  a  Cat  ?  And  this  is  not 
merely  the  resemblance  of  one  carnivorous  ani- 
mal to  another;  for  no  one  was  ever  reminded 
of  a  Dog  or  Wolf  by  a  Lion. 

Again,  all  the  Horses  and  Donkeys  neigh ;  for 
the  bray  of  the  Donkey  is  only  a  harsher  neigh, 
pitched  on  a  different  key,  it  is  true,  but  a  sound 
of  the  same  character,  —  as  the  Donkey  himself 
is  but  a  clumsy  and  dwarfish  Horse.  All  the 
Cows  low,  from  the  Buffalo  roaming  the  prairie, 
the  Musk-Ox  of  the  Arctic  ice-fields,  or  the  Jack 
of  Asia,  to  the  Cattle  feeding  in  our  pastures. 

Among  the  Birds,  this  similarity  of  voice  in 
Families  is  still  more  marked.  We  need  only  re- 
call the  harsh  and  noisy  Parrots,  so  similar  in 
their  peculiar  utterance.  Or  take  as  an  example 
the  web-footed  Family,  —  do  not  all  the  Geese  and 
the  innumerable  host  of  Ducks  quack  ?  Does  not 
every  member  of  the  Crow  Family  caw,  whether 
it  be  the  Jackdaw,  the  Jay,  or  the  Magpie,  the  Rook 


FAMILY   CHAKACTERISTICS.  123 

in  some  green  rookery  of  the  Old  World,  or  the 
Crow  of  our  woods,  with  its  long,  melancholy 
caw  that  seems  to  make  the  silence  and  solitude 
deeper  ?  Compare  all  the  sweet  warblers  of  the 
Songster  Family,  —  the  Nightingales,  the  Thrush- 
es, the  Mocking-Birds,  the  Robins  ;  they  differ  in 
the  greater  or  less  perfection  of  their  note,  but 
the  same  kind  of  voice  runs  through  the  whole 
group. 

These  affinities  of  the  vocal  systems  among 
animals  form  a  subject  well  worthy  of  the  deep- 
est study,  not  only  as  another  character  by  which  to 
classify  the  Animal  Kingdom  correctly,  but  as  bear- 
ing indirectly  also  on  the  question  of  the  origin  of 
animals.  Can  we  suppose  that  characteristics  like 
these  have  been  communicated  from  one  animal 
to  another  ?  When  we  find  that  all  the  members 
of  one  zoological  Family,  however  widely  scat- 
tered over  the  surface  of  the  earth,  inhabiting 
different  continents  and  even  different  hemi- 
spheres, speak  with  one  voice,  must  we  not  believe 
that  they  have  originated  in  the  places  where 
they  now  occur  with  all  their  distinctive  pecu- 
liarities ?  Who  taught  the  American  Thrush  to 
sing  like  his  European  relative  ?  He  surely  did 
not  learn  it  from  his  cousin  over  the  waters. 
Those  who  would  have  us  believe  that  all  ani- 
mals have  originated  from  common  centres  and 
single  pairs,  and  have  been  thence  distributed 


124  FAMILY   CHARACTERISTICS. 

over  the  world,  will  find  it  difficult  to  explain 
the  tenacity  of  such  characters,  and  their  recur- 
rence and  repetition  under  circumstances  that 
seem  to  preclude  the  possibility  of  any  commu- 
nication, on  any  other  supposition  than  that  of 
their  creation  in  the  different  regions  where  they 
are  now  found.  We  have  much  yet  to  learn  from 
investigations  of  this  kind,  with  reference  not 
only  to  Families  among  animals,  but  to  nation- 
alities among  men  also.  I  trust  that  the  nature 
of  languages  will  teach  us  as  much  about  the 
origin  of  the  races,  as  the  vocal  system  of  the 
animals  may  one  day  teach  us  about  the  origin 
of  the  different  groups  of  animals.  At  all  events, 
similarity  of  vocal  utterance  among  animals  is 
not  indicative  of  identity  of  Species ;  I  doubt, 
therefore,  whether  similarity  of  speech  proves 
community  of  origin  among  men. 

The  similarity  of  motion  in  Families  is  another 
subject  well  worth  the  consideration  of  the  nat- 
uralist :  the  soaring  of  the  Birds  of  Prey,  —  the 
heavy  napping  of  the  wings  in  the  Gallinaceous 
Birds,  —  the  floating  of  the  Swallows,  with  their 
short  cuts  and  angular  turns,  —  the  hopping  of 
the  Sparrows,  —  the  deliberate  walk  of  the  Hens 
and  the  strut  of  the  Cocks,  —  the  waddle  of  the 
Ducks  and  Geese,  —  the  slow,  heavy  creeping  of 
the  Land-Turtle,  —  the  graceful  flight  of  the 
Sea-Turtle  under  the  water,  —  the  leaping  and 


FAMILY   CHAEACTERISTICS.  125 

swimming  of  the  Frog,  —  the  swift  run  of  the 
Lizard,  like  a  flash  of  green  or  red  light  in  the 
sunshine,  —  the  lateral  undulation  of  the  Ser- 
pent, —  the  dart  of  the  Pickerel,  —  the  leap  of 
the  Trout,  —  the  rush  of  the  Hawk-Moth  through 
the  air,  —  the  fluttering  flight  of  the  Butterfly, 

—  the  quivering  poise  of  the  Humming-Bird, — 
the  arrow-like  shooting  of  the  Squid  through  the 
water,  —  the  slow  crawling  of  the  Snail  on  the 
land,  —  the  sideway  movement  of  the  Sand-Crab, 

—  the   backward   walk   of    the    Crawfish,  —  the 
almost  imperceptible  gliding  of  the  Sea-Anemone 
over  the  rock,  —  the  graceful,  rapid  motion  of  the 
Pleurobrachia,  with  its  endless  change  of  curve 
and  spiral.     In  short,  every  Family  of  animals 
has  its  characteristic    action    and   its    peculiar 
voice ;  and  yet  so  little  is  this  endless  variety 
of   rhythm   and    cadence   both   of    motion   and 
sound  in  the  organic  world  understood,  that  we 
lack  words  to  express  one  half  its  richness  and 
beauty. 


126  THE   CHARACTERS   OF   GENERA. 


CHAPTER  IX. 

THE   CHARACTERS   OF   GENERA. 

THE  well-known  meaning  of  the  words  generic 
and  specific  may  serve,  in  the  absence  of  a  more 
precise  definition,  to  express  the  relative  impor- 
tance of  those  groups  of  animals  called  Genera 
and  Species  in  our  scientific  systems.  The  Genus 
is  the  more  comprehensive  of  the  two  kinds  of 
groups,  while  the  Species  is  the  most  precisely 
defined,  or  at  least  the  most  easily  recognized, 
of  all  the  divisions  of  the  Animal  Kingdom. 
But  neither  the  term  Genus  nor  Species  has 
always  been  taken  in  the  same  sense.  Genus  es- 
pecially has  varied  in  its  acceptation,  from  the 
time  when  Aristotle  applied  it  indiscriminately 
to  any  kind  of  comprehensive  group,  from  the 
Classes  down  to  what  we  commonly  call  Genera, 
till  the  present  day. 

But  we  have  already  seen,  that,  instead  of 
calling  all  the  more  comprehensive  divisions  by 
the  name  of  Genera,  modern  science  has  applied 
special  names  to  each  of  them,  and  we  have  now 
Families,  Orders,  Classes,  and  Branches  above 


THE   CHARACTEKS   OF   GENERA.  127 

Genera  proper.  If  the  foregoing  discussion  upon 
the  nature  of  these  groups  is  based  upon  trust- 
worthy principles,  we  must  admit  that  they  are 
all  founded  upon  distinct  categories  of  characters, 
—  the  primary  divisions,  or  the  Branches,  upon 
plan  of  structure,  the  Classes  upon  the  manner 
of  its  execution,  the  Orders  upon  the  greater 
or  less  complication  of  a  given  mode  of  execu- 
tion, the  Families  upon  form ;  and  it  now  re- 
mains to  be  ascertained  whether  Genera  also 
exist  in  Nature,  and  by  what  kind  of  character- 
istics they  may  be  distinguished. 

Taking  the  practice  of  the  ablest  naturalists 
in  discriminating  Genera  as  a  guide  in  our  esti- 
mation of  their  true  nature,  we  must,  neverthe- 
less, remember  that  even  now,  while  their  classi- 
fications of  the  more  comprehensive  groups  usu- 
ally agree,  they  differ  greatly  in  their  limitation 
of  Genera,  so  that  the  Genera  of  some  authors 
correspond  to  the  Families  of  others,  and  vice 
versa.  This  undoubtedly  arises  from  the  absence 
of  a  definite  standard  for  the  estimation  of  these 
divisions.  But  the  different  categories  of  struct- 
ure forming  the  distinctive  criteria  of  the  more 
comprehensive  divisions  once  established,  the 
question  is  narrowed  down  to  an  inquiry  into  the 
special  category  upon  which  Genera  may  be  de- 
termined ;  and  if  this  can  be  accurately  defined, 
no  difference  of  opinion  need  interfere  hereaf- 
ter with  their  uniform  limitation. 


128  THE   CHARACTERS   OF   GENERA. 

Considering  all  these  divisions  of  the  Animal 
Kingdom  from  this  point  of  view,  it  is  evident 
that  the  more  comprehensive  ones  must  be  those 
which  are  based  on  the  broadest  characters, — 
the  Branches,  as  united  upon  plan  of  structure, 
standing  of  course  at  the  head ;  next  to  these 
the  Classes,  since  the  general  mode  of  executing 
the  plan  presents  a  wider  category  of  characters 
than  the  complication  of  structure  on  which  Or- 
ders rest;  after  Orders  come  Families,  or  the 
patterns  of  form  in  which  these  greater  or  less 
complications  of  structure  are  clothed  ;  and,  pro- 
ceeding in  the  same  way  from  more  general  to 
more  special  considerations,  we  can  have  no  other 
category  of  structure  as  characteristic  of  Genera 
than  the  details  of  structure  by  which  members 
of  the  same  Family  may  differ  from  each  other, 
and  this  I  consider  as  the  only  true  basis  on 
which  to  limit  Genera,  while  it  is  at  the  same 
time  in  perfect  accordance  with  the  practice  of 
the  most  eminent  modern  zoologists.  It  is  in 
this  way  that  Cuvier  has  distinguished  the  large 
number  of  Genera  he  has  characterized  in  his 
great  Natural  History  of  the  Fishes,  published 
in  connection  with  Valenciennes.  Latreille  has 
done  the  same  for  the  Crustacea  and  Insects  ;  and 
Milne-Edwards,  with  the  co-operation  of  Haime, 
has  recently  proceeded  upon  the  same  principle  in 
characterizing  a  great  number  of  Genera  among 


THE  CHARACTERS  OF   GENERA.  129 

the  Corals.  Many  others  have  followed  this  ex- 
ample, but  few  have  kept  in  view  the  necessity  of 
a  uniform  mode  of  proceeding,  or,  if  they  have 
done  so,  their  researches  have  covered  too  limit- 
ed a  ground  to  be  taken  into  consideration  in  a 
discussion  of  principles. 

It  is,  in  fact,  only  when  extending  over  a 
whole  Class  that  the  study  of  Genera  acquires  a 
truly  scientific  importance,  as  it  then  shows,  in  a 
connected  manner,  in  what  way,  by  what  features, 
and  to  what  extent  a  large  number  of  animals 
are  closely  linked  together  in  Nature.  Con- 
sidering  the  Animal  Kingdom  as  a  single  com- 
plete work  of  one  Creative  Intellect,  consistent 
throughout,  such  keen  analysis  and  close  criti- 
cism of  all  its  parts  have  the  same  kind  of  inter- 
est, in  a  higher  degree,  as  that  which  attaches  to 
other  studies  undertaken  in  the  spirit  of  careful 
comparative  research.  These  different  categories 
of  characters  are,  as  it  were,  different  peculiari- 
ties of  style  in  the  author,  different  modes  of 
treating  the  same  material,  new  combinations  of 
evidence  bearing  on  the  same  general  principles. 
The  study  of  Genera  is  a  department  of  Natural 
History  which  thus  far  has  received  too  little  at- 
tention even  at  the  hands  of  our  best  zoologists, 
and  has  been  treated  in  the  most  arbitrary  man- 
ner ;  it  should  henceforth  be  made  a  philosophical 
investigation  into  the  closer  affinities  which  natr 


130      THE  CHARACTERS  OF  GENERA. 

urally  bind  all  the  representatives  of  a  natural 
Family  in  minor  groups. 

Genera,  then,  are  divisions  of  a  more  restricted 
character  than  any  of  those  we  have  examined 
thus  far.  Some  of  them  include  only  one  Spe- 
cies, while  others  comprise  hundreds ;  since  cer- 
tain definite  combinations  of  characters  may  be 
limited  to  a  single  Species,  while  other  combina- 
tions may  be  repeated  in  many.  We  have  strik- 
ing examples  of  this  among  Birds :  the  Ostrich 
stands  alone  in  its  Genus,  while  the  number  of 
Species  among  the  Warblers  is  very  great. 
Among  Mammalia  the  Giraffe  also  stands  alone, 
while  Mice  and  Squirrels  include  many  Species. 
Genera  are  founded,  not,  as  we  have  seen,  on 
general  structural  characters,  but  on  the  finish  of 
special  parts,  as,  for  instance,  on  the  dentition. 
The  Cats  have  only  four  grinders  in  the  upper 
jaw  and  three  in  the  lower,  while  the  Hyenas 
have  one  more  above  and  below,  and  the  Dogs 
and  Wolves  have  two  more  above  and  two  more 
below.  In  the  last,  some  of  the  teeth  have  also 
flat  surfaces  for  crushing  the  food,  adapted  es- 
pecially to  their  habits,  since  they  live  on  vegeta- 
ble as  well  as  animal  substances.  The  formation 
of  the  claws  is  another  generic  feature.  There 
is  a  curious  example  with  reference  to  this  in  the 
Cheetah,  which  is  again  a  Genus  containing  only 
one  Species.  It  belongs  to  the  Cat  Family,  but 


THE  CHARACTERS  OF  GENERA.       131 

differs  from  ordinary  Lions  and  Tigers  in  having 
its  claws  so  constructed  that  it  cannot  draw  them 
back  over  the  paws,  though  in  every  other  re- 
spect they  are  like  the  claws  of  all  the  Cats. 
But  while  it  has  the  Cat-like  claw,  its  paws  are 
like  those  of  the  Dog,  and  this  singular  combina- 
tion of  features  is  in  direct  relation  to  its  habits, 
for  it  does  not  lie  in  wait  and  spring  upon  its 
prey  like  the  Cat,  but  hunts  it  like  the  Dog. 

While  Genera  themselves  are,  like  Families, 
easily  distinguished,  the  characters  on  which 
they  are  founded,  like  those  of  Families,  are 
difficult  to  trace.  There  are  often  features  be- 
longing to  these  groups  which  attract  the  atten- 
tion and  suggest  their  association,  though  they 
are  not  those  which  may  be  truly  considered 
generic  characters.  It  is  easy  to  distinguish  the 
Foxes,  for  instance,  by  their  bushy  tail,  and 
yet  that  is  no  true  generic  character ;  the  collar 
of  feathers  round  the  neck  of  the  Yultures  leads 
us  at  once  to  separate  them  from  the  Eagles,  but 
it  is  not  the  collar  that  truly  marks  the  Genus, 
but  rather  the  peculiar  structure  of  the  feathers 
which  form  it.  No  Bird  has  a  more  striking 
plumage  than  the  Peacock,  but  it  is  not  the  ap- 
pearance merely  of  its  crest  and  spreading  fan 
that  constitutes  the  Genus,  but  the  peculiar  struc- 
ture of  the  feathers.  Thousands  of  examples 
might  be  quoted  to  show  how  easily  Genera  may 


132  THE   CHARACTEES   0*    GENERA. 

be  singled  out,  named,  and  entered  in  our  sys- 
tems, without  being  duly  characterized,  and  it  is 
much  to  be  lamented  that  there  is  no  possibility 
of  checking  the  loose  work  of  this  kind  with  which 
the  annals  of  our  science  are  daily  flooded. 

It  would,  of  course,  be  quite  inappropriate  to 
present  here  any  general  revision  of  these  groups  ; 
but  I  may  present  a  few  instances  to  illustrate 
the  principle  of  their  classification,  and  to  show 
on  what  characters  they  are  properly  based. 
Among  Reptiles,  we  find,  for  instance,  that  the 
Genera  of  our  fresh-water  Turtles  differ  from 
each  other  in  the  cut  of  their  bill,  in  the  arrange- 
ment of  their  scales,  in  the  form  of  their  claws, 
etc.  Among  Fishes,  the  different  Genera  includ- 
ed under  the  Family  of  Perches  are  distinguished 
by  the  arrangement  of  their  teeth,  by  the  serra- 
tures  of  their  gill-covers  and  of  the  arch  to 
which  the  pectoral  fins  are  attached,  by  the  na- 
ture and  combination  of  the  rays  of  their  fins, 
by  the  structure  of  their  scales,  etc.  Among  In- 
sects, the  various  Genera  of  the  Butterflies  differ 
in  the  combination  of  the  little  rods  which  sustain 
their  wings,  in  the  form  and  structure  of  their 
antennae,  of  their  feet,  of  the  minute  scales 
which  cover  their  wings,  etc.  Among  Crustacea, 
the  Genera  of  Shrimps  vary  in  the  form  of  the 
claws,  in  the  structure  of  the  parts  of  the  mouth, 
in  the  articulations  of  their  feelers,  etc.  Among 


THE   CHARACTERS   OF   GENERA.  133 

Worms,  the  different  Genera  of  the  Leech  Fam- 
ily are  combined  upon  the  form  of  the  disks  by 
which  they  attach  themselves,  upon  the  number 
and  arrangement  of  their  eyes,  upon  the  struc- 
ture of  the  hard  parts  with  which  the  mouth  is 
armed,  etc.  Among  Cephalopods,  the  Family  of 
Squids  contains  several  Genera  distinguished  by 
the  structure  of  the  solid  shield  within  the  skin 
of  the  back,  by  the  form  and  connection  of  their 
fins,  by  the  structure  of  the  suckers  with  which 
their  arms  are  provided,  by  the  form  of  their 
beak,  etc.  In  every  Class,  we  find  throughout 
the  Animal  Kingdom  that  there  is  no  sound  basis 
for  the  discrimination  of  Genera  except  the  de- 
tails of  their  structure ;  but  in  order  to  define 
them  accurately  an  extensive  comparison  of  them 
is  indispensable,  and  in  characterizing  them  only 
such  features  should  be  enumerated  as  are  truly 
generic ;  whereas,  in  the  present  superficial  meth- 
od of  describing  genera,  features  are  frequently 
introduced  which  belong  not  only  to  the  whole 
Family,  but  even  to  the  whole  Class  which  in- 
cludes them. 


134          SPECIES  AND  BREEDS. 


CHAPTER    X. 

SPECIES  AND  BREEDS. 

THERE  remains  but  one  more  division  of  the 
Animal  Kingdom  for  our  consideration,  the  most 
limited  of  all  in  its  circumscription,  —  that  of 
Species.  It  is  with  the  study  of  this  kind  of 
group  that  naturalists  generally  begin  their  inves- 
tigations. I  believe,  however,  that  the  study  of 
Species  as  the  basis  of  a  scientific  education  is  a 
great  mistake.  It  leads  us  to  overrate  the  value  of 
Species,  and  to  believe  that  they  exist  in  Nature 
in  some  different  sense  from  the  other  groups  ;  as 
if  there  were  something  more  real  and  tangible  in 
Species  than  in  Genera, .Families,  Orders,  Classes, 
or  Branches.  The  truth  is,  that  to  study  a  vast 
number  of  Species  without  tracing  the  principles 
that  combine  them  under  more  comprehensive 
groups  is  only  to  burden  the  mind  with  discon- 
nected facts,  and  more  may  be  learned  by  a  faith- 
ful and  careful  comparison  of  a  few  Species  than 
by  a  more  cursory  examination  of  a  greater 
number.  When  one  considers  the  immense 
number  of  Species  already  known,  naturalists 


SPECIES  AND  BREEDS.          135 

might  well  despair  of  becoming  acquainted  with 
them  all,  were  they  not  constructed  on  a  few 
fundamental  patterns,  so  that  the  study  of  one 
Species  teaches  us  a  great  deal  for  all  the  rest. 
De  Candolle,  who  was  at  the  same  time  a  great  bot- 
anist and  a  great  teacher,  told  me  once  that  he 
could  undertake  to  illustrate  the  fundamental 
principles  of  his  science  with  the  aid  of  a  dozen 
plants  judiciously  selected,  and  that  it  was  his 
unvarying  practice  to  induce  students  to  make  a 
thorough  study  of  a  few  minor  groups  of  plants, 
in  all  their  relations  to  one  another,  rather  than 
to  attempt  to  gain  a  superficial  acquaintance  with 
a  large  number  of  species.  The  powerful  influ- 
ence he  has  had  upon  the  progress  of  Botany 
vouches  for  the  correctness  of  his  views.  Indeed, 
every  profound  scholar  knows  that  sound  learn- 
ing can  be  attained  only  by  this  method,  and  the 
study  of  Nature  makes  no  exception  to  the  rule. 
I  would  therefore  advise  every  student  to  select 
a  few  representatives  from  all  the  Classes,  and  to 
study  these  not  only  with  reference  to  their  spe- 
cific characters,  but  as  members  also  of  a  Genus, 
of  a  Family,  of  an  Order,  of  a  Class,  and  of  a 
Branch.  He  will  soon  convince  himself  that 
Species  have  no  more  definite  and  real  existence 
in  Nature  than  all  the  other  divisions  of  the  An- 
imal Kingdom,  and  that  every  animal  is  the  rep- 
resentative of  its  Branch,  Class,  Order,  Family, 


136          SPECIES  AND  BREEDS. 

and  Genus  as  much  as  of  its  Species.  Specific 
characters  are  only  those  determining  size,  pro- 
portion, color,  habits,  and  relations  to  surround- 
ing circumstances  and  external  objects.  How 
superficial,  then,  must  be  any  one's  knowledge  of 
an  animal  who  studies  it  only  with  relation  to  its 
specific  characters !  He  will  know  nothing  of  the 
finish  of  special  parts  of  the  body,  —  nothing  of 
the  relations  between  its  form  and  its  structure, 

—  nothing  of  the  relative  complication  of  its  or- 
ganization as  compared  with  other  allied  animals, 

—  nothing  of  the  general  mode  of  execution  of 
its  structure,  —  nothing  of  the  general  plan  of 
structure  expressed  in  that  mode  of  execution. 
Yet,  with  the  exception  of  the  ordinal  charac- 
ters, which,  since  they  imply  relative  superiority 
and  inferiority,  require,  of  course,  a  number  of 
specimens  for  comparison,  his  one  animal  would 
tell  him  all  this  as  well  as  the  specific  characters. 

All  the  more  comprehensive  groups,  equally 
with  Species,  are  based  upon  a  positive,  perma- 
nent, specific  principle,  maintained  generation 
after  generation  with  all  its  essential  characteris- 
tics. Individuals  are  the  transient  representa- 
tives of  all  these  organic  principles,  which  cer- 
tainly have  an  independent,  immaterial  existence, 
since  they  outlive  the  individuals  that  embody 
them,  and  are  no  less  real  after  the  generation 
that  has  represented  them  for  a  time  has  passed 
away,  than  they  were  before. 


SPECIES  AND   BREEDS.  137 

From  a  comparison  of  a  number  of  well-known 
Species  belonging  to  a  natural  Genus,  it  is  not 
difficult  to  ascertain  what  are  essentially  specific 
characters.  There  is  hardly  among  Mammalia  a 
more  natural  Genus  than  that  which  includes  the 
Rabbits  and  Hares,  or  that  to  which  the  Rats  and 
Mice  are  referred.  Let  us  see  how  the  different 
Species  differ  from  one  another.  Though  we 
give  two  names  in  the  vernacular  to  the  Genus 
Hare,  both  Hares  and  Rabbits  agree  in  all  the 
structural  peculiarities  constituting  a  Genus ; 
but  the  different  Species  are  distinguished  by 
their  absolute  size  when  full-grown,  —  by  the  na- 
ture and  color  of  their  fur,  —  by  the  size  and 
form  of  the  ear,  —  by  the  relative  length  of  their 
legs  and  tail,  —  by  the  more  or  less  slender  build 
of  their  whole  body,  —  by  their  habits,  some  liv- 
ing in  open  grounds,  others  among  the  bushes, 
others  in  swamps,  others  burrowing  under  the 
earth,  —  by  the  number  of  young  they  bring 
forth,  —  by  their  different  seasons  of  breeding, — 
and  by  still  minor  differences,  such  as  the  perma- 
nent color  of  the  hair  throughout  the  year  in 
some,  while  in  others  it  turns  white  in  winter. 
The  Rats  and  Mice  differ  in  a  similar  way  :  there 
being  large  and  small  Species,  —  some  gray,  some 
brown,  others  rust-colored, — some  with  soft, 
others  with  coarse  hair ;  they  differ  also  in  the 
length  of  the  tail,  and  in  having  it  more  or  less 


138          SPECIES  AND  BREEDS. 

covered  with  hair,  —  in  the  cut  of  the  ears,  and 
their  size, — in  the  length  of  their  limbs,  which 
are  slender  and  long  in  some,  short  and  thick  in 
others,  —  in  their  various  ways  of  living,  —  in  the 
different  substances  on  which  they  feed,  —  and 
also  in  their  distribution  over  the  surface  of  the 
earth,  whether  circumscribed  within  certain  lim- 
ited areas  or  scattered  over  a  wider  range. 

What  is  now  the  nature  of  these  differences  by 
which  we  distinguish  Species  ?  They  are  totally 
distinct  from  any  of  the  categories  on  which  Gen- 
era, Families,  Orders,  Classes,  or  Branches  are 
founded,  and  may  readily  be  reduced  to  a  few 
heads.  They  are  differences  in  the  proportion  of 
the  parts  and  in  the  absolute  size  of  the  whole 
animal,  in  the  color  and  general  ornamentation 
of  the  surface  of  the  body,  and  in  the  relations 
of  the  individuals  to  one  another  and  to  the 
world  around.  A  farther  analysis  of  other  Gen- 
era would  show  us  that  among  Birds,  Reptiles, 
Fishes,  and,  in  fact,  throughout  the  Animal  King- 
dom, Species  of  well-defined  natural  Genera  dif- 
fer in  the  same  way.  We  are  therefore  justified 
in  saying  that  the  category  of  characters  on 
which  Species  are  based  implies  no  structural 
differences,  but  presents  the  same  structure  com- 
bined under  certain  minor  differences  of  size, 
proportion,  and  habits.  All  the  specific  characters 
stand  in  direct  reference  to  the  generic  structure, 


SPECIES   AND   BREEDS.  139 

the  family  form,  the  ordinal  complication  of 
structure,  the  mode  of  execution  of  the  Class, 
and  the  plan  of  structure  of  the  Branch,  all  of 
which  are  embodied  in  the  frame  of  each  individ- 
ual in  each  Species,  even  though  all  these  indi- 
viduals are  constantly  reproducing  others  and 
dying  away ;  so  that  the  specific  characters  have 
no  more  permanency  in  the  individuals  than 
those  which  characterize  the  Genus,  the  Family, 
the  Order,  the  Class,  and  the  Branch.  I  believe, 
therefore,  that  naturalists  have  been  entirely 
wrong  in  considering  the  more  comprehensive 
groups  to  be  theoretical,  and  in  a  measure  arbi- 
trary,—  that  is,  an  attempt  of  certain  men  to 
classify  the  Animal  Kingdom  according  to  their 
individual  views,  —  while  they  have  ascribed  to 
Species,  as  contrasted  with  the  other  divisions,  a 
more  positive  existence  in  Nature. 

No  further  argument  is  needed  to  show  that  it 
is  not  only  the  Species  that  lives  in  the  individ- 
ual, but  that  every  individual,  though  belonging 
to  a  distinct  Species,  is  built  upon  a  precise  and 
definite  plan  which  characterizes  its  Branch, — 
that  that  plan  is  executed  in  each  individual  in  a 
particular  way  which  characterizes  its  Class, — 
that  every  individual  with  its  kindred  occupies  a 
definite  position  in  a  series  of  structural  compli- 
cations which  characterizes  its  Order,  —  that  in 
every  individual  all  these  structural  features  are 


140          SPECIES  AND  BREEDS. 

combined  under  a  definite  pattern  of  form  which 
characterizes  its  Family,  —  that  every  individual 
exhibits  structural  details  in  the  finish  of  its  parts 
which  characterize  its  Genus,  —  and  finally  that 
every  individual  presents  certain  peculiarities  in 
the  proportion  of  its  parts,  in  its  color,  in  its  size, 
in  its  relations  to  its  fellow-beings  and  the  sur- 
rounding objects,  which  constitute  its  specific 
characters ;  and  all  this  is  repeated  in  the  same 
kind  of  combination,  generation  after  generation, 
while  the  individuals  themselves  die.  If  we  ac- 
cept these  propositions,  which  seem  to  me  self- 
evident,  it  is  impossible  to  avoid  the  conclusion 
that  Species  do  not  exist  in  Nature  in  any  other 
sense  than  the  more  comprehensive  groups  of  the 
zoological  system. 

There  is  one  question  respecting  Species  that 
gives  rise  to  very  earnest  discussions  in  our  day, 
not  only  among  naturalists,  but  among  all 
thinking  people.  How  far  are  they  permanent, 
and  how  far  mutable  ?  With  reference  to  the 
permanence  of  Species,  there  is  much  to  be 
learned  from  the  geological  phenomena  belong- 
ing to  our  own  period,  in  as  far  as  they  bear 
witness  to  the  invariability  of  types  during  hun- 
dreds of  thousands  of  years  at  least.  I  hope  to 
present  a  part  of  this  evidence  in  a  future  article 
upon  Coral  Reefs,  but  in  the  mean  time  I  cannot 
leave  this  subject  without  touching  upon  a  point 


SPECIES  AND  BREEDS.          141 

which  has  been  urged  with  great  persistency  in 
recent  discussions.  I  refer  to  the  variability  of 
Species  as  shown  in  domestication. 

The  domesticated  animals  with  their  numer- 
ous breeds  are  constantly  adduced  as  evidence 
of  the  changes  which  animals  may  undergo,  and 
as  furnishing  hints  respecting  the  way  in  which 
the  diversity  now  observed  among  animals  may 
have  been  produced.  It  is  my  conviction  that 
such  inferences  are  in  no  way  sustained  by  the 
facts  of  the  case,  and  that,  however  striking  the 
differences  may  be  between  the  breeds  of  our 
domesticated  animals,  as  compared  with  the  wild 
Species  of  the  same  Genus,  they  are  of  a  peculiar 
character,  entirely  distinct  from  the  features  pre- 
vailing among  the  latter,  and  altogether  incident 
to  the  circumstances  under  which  they  appear. 
By  this  I  do  not  mean  the  natural  action  of  phys- 
ical conditions,  but  the  more  or  less  intelligent 
direction  of  the  circumstances  under  which  they 
live.  The  inference  drawn  from  the  varieties  in- 
troduced among  animals  in  a  state  of  domestica- 
tion, with  reference  to  the  origin  of  Species,  is 
usually  this :  that  what  the  farmer  does  on  a 
small  scale  Nature  may  do  on  a  large  one.  It  is 
true  that  man  has  been  able  to  produce  certain 
changes  in  the  animals  under  his  care,  and  that 
these  changes  have  resulted  in  a  variety  of  breeds. 
But  in  doing  this,  he  has,  in  my  estimation,  in 


142  SPECIES   AND   BREEDS. 

no  way  altered  the  character  of  the  Species,  but 
only  developed  its  pliability  under  the  will  of  man, 
that  is,  under  a  power  similar  in  its  nature  and 
mode  of  action  to  that  power  to  which  animals  owe 
their  very  existence.  The  influence  of  man  up- 
on animals  is,  in  other  words,  the  action  of  mind 
upon  them ;  and  yet  the  ordinary  mode  of  argu- 
ing upon  this  subject  is,  that,  because  the  intelli- 
gence of  man  has  been  able  to  produce  certain 
varieties  in  domesticated  animals,  therefore  phys- 
ical causes  have  produced  all  the  diversity  exist- 
ing among  wild  ones.  Surely,  the  sounder  logic 
would  be  to  infer,  that,  because  our  finite  intel- 
ligence may  cause  the  original  pattern  to  vary 
by  some  slight  shades  of  difference,  therefore  a 
superior  intelligence  must  have  established  all  the 
boundless  diversity  of  which  our  boasted  varieties 
are  but  the  faintest  echo.  It  is  the  most  intelli- 
gent farmer  who  has  the  greatest  success  in  im- 
proving his  breeds  ;  and  if  the  animals  he  lias  so 
fostered  are  left  to  themselves  without  that  intel- 
ligent care,  they  return  to  their  normal  condition. 
So  with  plants  :  the  shrewd,  observing,  thought- 
ful gardener  will  obtain  many  varieties  from  his 
flowers ;  but  those  varieties  will  fade  out,  if  left 
to  themselves.  There  is,  as  it  were,  a  certain 
degree  of  pliability  and  docility  in  the  organiza- 
tion both  of  animals  and  plants,  which  may  be 
developed  by  the  fostering  care  of  man,  and  with- 


SPECIES  AND  BREEDS.          143 

in  which  he  can  exercise  a  certain  influence  ;  bnt 
the  variations  thus  produced  are  of  a  peculiar 
kind,  and  do  not  correspond  to  the  differences 
of  the  wild  Species.  Let  us  take  some  examples 
to  illustrate  this  assertion. 

Every  Species  of  wild  Bull  differs  from  the 
others  in  its  size ;  but  all  the  individuals  corre- 
spond to  the  average  standard  of  size  characteris- 
tic of  their  respective  Species,  and  show  none  of 
those  extreme  differences  of  size  so  remarkable 
among  our  domestic  Cattle.  Every  Species  of  wild 
Bull  has  its  peculiar  color,  and  all  the  individuals 
of  one  Species  share  in  it:  not  so  with  our  do- 
mesticated Cattle,  among  which  every  individual 
may  differ  in  color  from  every. other.  All  the  in- 
dividuals of  the  same  Species  of  wild  Bull  agree 
in  the  proportion  of  their  parts,  in  the  mode  of 
growth  of  the  hair,  in  its  quality,  whether  fine  or 
soft :  not  so  with  our  domesticated  Cattle,  among 
which  we  find  in  the  same  Species  overgrown 
and  dwarfish  individuals,  those  with  long  and 
short  legs,  with  slender  and  stout  build  of  the 
body,  with  horns  or  without,  as  well  as  the  great- 
est variety  in  the  mode  of  twisting  the,  horns,  — 
in  short,  the  widest  extremes  of  development 
which  the  degree  of  pliability  in  that  Species 
will  allow. 

A  curious  instance  of  the  power  of  man,  not 
only  in  developing  the  pliability  of  an  animal's 


144          SPECIES  AND  BREEDS. 

organization,  but  in  adapting  it  to  suit  his  own 
caprices,  is  that  of  the  Golden  Carp,  so  frequently 
seen  in  bowls  and  tanks  as  the  ornament  of  draw- 
ing-rooms and  gardens.  Not  only  an  infinite 
variety  of  spotted,  striped,  variegated  colors  has 
been  produced  in  these  Fishes,  but,  especially 
among  the  Chinese,  so  famous  for  their  morbid 
love  of  whatever  is  distorted  and  warped  from  its 
natural  shape  and  appearance,  all  sorts  of  changes 
have  been  brought  about  in  this  single  Species. 
A  book  of  Chinese  paintings,  showing  the  Golden 
Carp  in  its  varieties,  represents  some  as  short  and 
stout,  others  long  and  slender,  —  some  with  the 
ventral  side  swollen,  others  hunchbacked, — some 
with  the  mouth  greatly  enlarged,  while  in  others 
.the  caudal  fin,  which,  in  the  normal  condition 
of  the  Species,  is  placed  vertically  at  the  end  of 
the  tail,  and  is  forked  like  those  of  other  Fishes, 
has  become  crested  and  arched,  or  is  double  or 
crooked,  or  has  swerved  in  some  other  way  from 
its  original  pattern.  But,  in  all  these  variations, 
there  is  nothing  which'  recalls  the  characteristic 
specific  differences  among  the  representatives  of 
the  Carp  Family,  which,  in  their  wild  state,  are 
very  monotonous  in  their  appearance  all  the 
world  over. 

Were  it  appropriate  to  accumulate  evidence 
here  upon  this  subject,  I  could  bring  forward 
many  more  examples  quite  as  striking  as  those 


SPECIES  AND  BEEEDS.          145 

above  mentioned.  The  various  breeds  of  our 
domesticated  Horses  present  the  same  kind  of 
irregularities,  and  do  not  differ  from  each  other 
in  the  same  way  as  the  wild  Species  differ  from 
one  another.  Or  take  the  Genus  Dog :  the  differ- 
ences between  its  wild  Species  do  not  correspond 
in  the  least  with  the  differences  observed  among 
the  domesticated  ones.  Compare  the  differences 
between  the  various  kinds  of  Jackals  and  Wolves 
with  those  that  exist  between  the  Bull-Dog  and 
Greyhound,  for  instance,  or  between  the  St. 
Charles  and  the  Terrier,  or  between  the  Esqui- 
maux and  the  Newfoundland  Dog.  I  need 
hardly  add,  that  what  is  true  of  the  Horses, 
the  Cattle,  the  Dogs,  is  true  also  of  the  Donkey, 
the  Goat,  the  Sheep,  the  Pig,  the  Cat,  the  Rabbit, 
the  different  kinds  of  barn-yard  fowl,  —  in  short, 
of  all  those  animals  that  are  in  domesticity  the 
chosen  companions  of  man. 

In  fact,  all  the  variability  among  domesticated 
Species  is  due  to  the  fostering  care,  or,  in  its 
more  extravagant  freaks,  to  the  fancies  of  man ; 
and  it  has  never  been  observed  in  the  wild  Species, 
where,  on  the  contrary,  everything  shows  the 
closest  adherence  to  the  distinct,  well-defined, 
and  invariable  limits  of  the  Species.  It  surely 
does  not  follow,  that,  because  the  Chinese  can, 
under  abnormal  conditions,  produce  a  variety  of 
fantastic  shapes  in  the  Golden  Carp,  therefore 


146          SPECIES  AND  BREEDS. 

water,  or  the  physical  conditions  established  in 
the  water,  can  create  a  Fish,  any  more  than  it 
follows,  that,  because  they  can  dwarf  a  tree,  or 
alter  its  aspect,  by  stunting  its  growth  in  one 
direction,  and  forcing  it  in  another,  therefore  the 
earth,  or  the  physical  conditions  connected  with 
their  growth,  can  create  a  Pine,  an  Oak,  a  Birch, 
or  a  Maple. 

I  confess  that,  in  all  the  arguments  derived 
from  the  phenomena  of  domestication,  to  prove 
that  animals  owe  their  origin  and  diversity  to  the 
natural  action  of  the  conditions  under  which  they 
live,  the  conclusion  does  not  seem  to  me  to  follow 
logically  from  the  premises.  And  the  fact  that 
the  domesticated  animals  of  all  the  races  of  men, 
equally  with  the  white  race,  vary  among  them- 
selves in  the  same  way,  and  differ  in  the  same 
way  from  the  wild  Species,  makes  it  still  more 
evident,  that  domesticated  varieties  do  not  ex- 
plain the  origin  of  Species,  except,  as  I  have  said, 
by  showing,  that  the  intelligent  will  of  man  can 
produce  effects  which 'physical  causes  have  never 
been  known  to  produce,  and  that  we  must,  there- 
fore, look  to  some  cause  outside  of  Nature,  cor- 
responding in  kind  to  the  intelligence  of  man, 
though  so  different  in  degree,  for  all  the  phe- 
nomena connected  with  the  existence  of  animals 
in  their  wild  state. 

So  far  from  attributing  these  original  differ- 


SPECIES   AND   BREEDS.  147 

ences  among  animals  to  natural  influences,  it 
would  seem,  that,  while  a  certain  freedom  of 
development  is  left,  within  the  limits  of  which 
man  can  exercise  his  intelligence  and  his  inge- 
nuity, not  even  this  superficial  influence  is  allowed 
to  physical  conditions  unaided  by  some  guiding 
power,  since,  in  their  normal  state,  the  wild  Species 
remain,  so  far  as  we  have  been  able  to  discover, 
entirely  unchanged,  —  maintained,  it  is  true,  in 
their  integrity  by  the  circumstances  established  for 
their  support,  but  never  altered  by  them.  Nature 
holds  inviolable  the  stamp  that  God  has  set  upon 
his  creatures ;  and  if  man  is  able  to  influence 
their  organization  in  some  slight  degree,  it  is 
because  the  Creator  has  given  to  his  relations 
with  the  animals  he  has  intended  for  his  com- 
panions the  same  plasticity  which  he  has  allowed 
to  every  other  side  of  his  life,  in  virtue  of  which 
he  may  in  some  sort  mould  and  shape  it  to  his 
own  ends,  and  be  helcl  responsible  also  for  its 
results. 

The  common  sense  of  a  civilized  community 
has.  already  pointed  out  the  true  distinction,  in 
applying  another  word  to  the  discrimination  of 
the  different  kinds  of  domesticated  animals. 
They  are  called  Breeds,  and  Breeds  among  ani- 
mals are  the  work  of  man :  Species  were  created 
by  God. 


148  FORMATION    OF   CORAL  REEFS. 


CHAPTER  XI. 

FORMATION  OF   CORAL  REEFS. 

AMONG  the  astounding  discoveries  of  modern 
science  is  that  of  the  immense  periods  which 
have  passed  in  the  gradual  formation  of  our 
earth.  So  vast  were  the  cycles  of  time  preceding 
even  the  appearance  of  man  on  the  surface  of 
our  globe,  that  our  own  period  seems  as  yester- 
day when  compared  with  the  epochs  that  have 
gone  before  it.  Had  we  only  the  evidence  of  the 
deposits  of  rock  heaped  above  each  other  in  regu- 
lar strata  by  the  slow  accumulation  of  mate- 
rials, they  alone  would  convince  us  of  the  long 
and  slow  maturing  of  God's  work  on  the  earth ; 
but  when  we  add  to  these  the  successive  popu- 
lations of  whose  life  •  this  world  has  been  the 
theatre,  and  whose  remains  are  hidden  in.  the 
rocks  into  which  the  mud  or  sand  or  soil  of  what- 
ever kind  on  which  they  lived  has  hardened  in 
the  course  of  time,  —  or  the  enormous  chains  of 
mountains  whose  upheaval  divided  these  periods 
of  quiet  accumulation  by  great  convulsions, — 
or  the  changes  of  a  different  nature  in  the  con- 


FORMATION  OF  COKAL  BEEFS.       149 

figuration  of  our  globe,  as  the  sinking  of  lands 
beneath  the  ocean,  or  the  gradual  rising  of  con- 
tinents and  islands  above  it,  —  or  the  wearing  of 
great  river-beds,  or  the  filling  of  extensive  water- 
basins,  till  marshes  first  and  then  dry  land  suc- 
ceeded to  inland  seas,  —  or  the  slow  growth  of 
coral  reefs,  those  wonderful  sea-walls  raised  by 
the  little  ocean-architects  whose  own  bodies  fur- 
nish both  the  building-stones  and  the  cement 
that  binds  them  together,  and  who  have  worked 
so  busily  during  the  long  centuries,  that  there 
are  extensive  countries,  mountain-chaiiis,  islands, 
and  long  lines  of  coast  consisting  solely  of  their 
remains,  —  or  the  countless  forests  that  must 
have  grown  up,  flourished,  died,  and  decayed, 
to  fill  the  storehouses  of  coal  that  feed  the  fires 
of  the  human  race  to-day,  —  if  we  consider  all 
these  records  of  the  past,  the  intellect  fails  to 
grasp  a  chronology  for  which  our  experience 
furnishes  no  data,  and  the  time  that  lies  behind 
us  seems  as  much  an  eternity  to  our  conception 
as  the  unknown  future  that  stretches  indefinitely 
before  us. 

The  physical  as  well  as  the  human  history  of 
the  world  has  its  mythical  age,  lying  dim  and 
vague  in  the  morning  mists  of  creation,  like  that 
of  the  heroes  and  demigods  in  the  early  tra- 
ditions of  man,  defying  all  our  ordinary  dates 
and  measures.  But  if  the  succession  of  periods 


150  FORMATION   OF  COKAL  KEEF.S. 

that  prepared  the  earth  for  the  coming  of  man, 
and  the  animals  and  plants  that  accompany  him 
on  earth,  baffles  our  finite  attempts  to  estimate 
its  duration,  have  we  any  means  of  determining 
even  approximately  the  length  of  the  period  to 
which  we  ourselves  belong?  If  so,  it  may  fur- 
nish us  with  some  data  for  the  further  solution 
of  these  wonderful  mysteries  of  time,  and  it  is 
besides  of  especial  importance  with  reference  to 
the  question  of  permanence  of  Species. 

Those  who  maintain  the  mutability  of  Species, 
and  accooint  for  all  the  variety  of  life  on  earth 
by  the  gradual  changes  wrought  by  time  and 
circumstances,  do  not  accept  historical  evidence 
as  affecting  the  question  at  all.  The  relics  of 
those  oldest  nations,  all  whose  history  is  pre- 
served in  monumental  records,  do  not  indicate 
the  slightest  variation  of  organic  types  from  the 
earliest  epoch  to  this  day.  The  animals  pre- 
served within  their  tombs  or  carved  upon  the 
walls  of  their  monuments  by  the  ancient  Egyp- 
tians were  the  same  as  those  that  have  their 
home  in  the  valley  of  the  Nile  to-day  ;  the 
negro,  whose  peculiar  features  are  unmistaka- 
ble even  in  their  rude  artistic  attempts  to  rep- 
resent them,  was  the  same  woolly-haired,  thick- 
lipped,  flat-nosed,  dark-skinned  being  in  the 
days  of  the  Rameses  that  he  is  now.  The 
Apis,  the  Ibis,  the  Crocodiles,  the  sacred  Beetles, 


FORMATION  OF  CORAL  REEFS.       151 

have  brought  down  to  us  unchanged  all  the  char- 
acters that  superstition  hallowed  in  those  early 
days.  The  stony  face  of  the  Sphinx  is  not  more 
true  to  its  past,  nor  the  massive  architecture 
of  the  Pyramids  more  unchanged,  than  they  are. 
But  the  advocates  of  the  mutability  of  Species 
say  truly  enough  that  the  most  ancient  traditions 
are  but  as  yesterday  in  the  world's  history,  and 
that  what  six  thousand  years  could  not  do  sixty 
thousand  years  might  effect.  Leaving  aside,  then, 
all  historical  chronology,  how  far  back  can  we 
trace  our  own  geological  period,  and  the  Species 
belonging  to  it  ?  By  what  means  can  we  deter- 
mine its  duration  ?  Within  what  limits,  by  what 
standard,  may  it  be  measured  ?  Shall  hundreds, 
or  thousands,  or  hundreds  of  thousands,  or  mil- 
lions of  years  be  the  unit  from  which  we  start  ? 

I  will  begin  this  inquiry  with  a  series  of  facts 
which  I  myself  have  had  an  opportunity  of  in- 
vestigating with  especial  care  respecting  the  for- 
mation and  growth  of  the  Coral  Reefs  of  Florida. 
But  first  a  few  words  on  Coral  Reefs  in  general. 
They  are  living  limestone  walls  built  up  from 
certain  depths  in  the  ocean  by  the  natural  growth 
of  a  variety  of  animals,  but  limited  by  the  level 
of  high  water,  beyond  which  they  cannot  rise, 
since  the  little  beings  that  compose  them  die  as 
soon  as  they  are  removed  from  the  vitalizing 
influence  of  the  pure  sea-water.  These  walls 


152       FORMATION  OF  COKAL  REEFS. 

have  a  variety  of  outlines :  they  may  be  straight, 
circular,  semicircular,  or  oblong,  according  to  the 
form  of  the  coast  along  which  the  little  Reef- 
Builders  establish  themselves ;  and  their  height 
is,  of  course,  determined  by  the  depth  of  the 
bottom  on  which  they  rest.  If  they  settle  about 
an  island  on  all  sides  of  which  the  conditions  for 
their  growth  are  equally  favorable,  they  will  raise 
a  wall  all  round  it,  thus  encircling  it  with  a  ring 
of  Coral  growth.  The  Athols  in  the  Pacific 
Ocean,  those  circular  islands  enclosing  sometimes 
a  fresh-water  lake  in  mid-ocean,  are  Coral  walls 
of  this  kind,  that  have  formed  a  ring  around  a 
central  island. 


This  is  easily  understood,  if  we  remember  that 
the  bottom  of  the  Pacific  Ocean  is  by  no  means 
a  stable  foundation  for  such  a  structure.  On 
the  contrary,  over  a  certain  area,  already  sur- 
veyed with  some  accuracy  by  Professor  Dana, 
during  the  United  States  Exploring  Expedition, 
it  is  subsiding  ;  and  if  an  island  upon  which 
the  Reef-Builders  have  established  themselves 


FORMATION  OF  CORAL  REEFS.       153 

be  situated  in  that  area  of  subsidence,  it  will, 
of  course,  sink  with  the  floor  on  which  it  rests, 
carrying  down  also  the  Coral  wall  to  a  greater 
depth  in  the  sea.  In  such  instances,  if  the  rate 


^JT\^ 

^WfifS^  ^llliHI!l(!f(!|J|(!l!l!lllil 

of  subsidence  be  more  rapid  than  the  rate  of 
growth  in  the  Corals,  the  island  and  the  wall 
itself  will  disappear  beneath  the  ocean.  But 
whenever,  on  the  contrary,  the  rate  of  increase 
in  the  wall  is  greater  than  that  of  subsidence  in 
the  island,  while  the  latter  gradually  sinks  below 
the  surface,  the  former  rises  in  proportion,  and 
by  the  time  it  has  completed  its  growth  the  cen- 
tral island  has  vanished,  and  there  remains  only 
a  ring  of  Coral  Reef,  with  here  and  there  a 
break  perhaps,  at  some  spot  where  the  more 
prosperous  growth  of  the  Corals  has  been  checked. 


If,  however,  as  sometimes  happens,  there  is  no 
such  break,  and  the  wall  is  perfectly  uninter- 
rupted, the  sheet  of  sea-water  so  enclosed  may 
be  changed  to  fresh  water  by  the  rains  that  are 
poured  into  it.  Such  a  water-basin  will  remain 

7* 


154       FORMATION  OF  CORAL  REEFS. 

salt,  it  is  true,  in  its  lower  part,  and  the  fact  that 
it  is  affected  by  the  rise  and  fall  of  the  tides 
shows  that  it  is  not  entirely  secluded  from  com- 
munication with  the  ocean  outside ;  but  the  salt 
water,  being  heavier,  sinks,  while  the  lighter 
rain-water  remains  above,  and  it  is  to  all  appear- 
ance actually  changed  into  a  fresh-water  lake. 

I  need  not  dwell  here  on  the  further  history 
of  such  a  Coral  island,  or  follow  it  through  the 
changes  by  which  the  summit  of  its  circular  wall 
becomes  covered  with  a  fertile  soil,  a  tropical 
vegetation  springs  up  upon  it,  and  it  is  at  last 
perhaps  inhabited  by  man.  There  is  something 
very  attractive  in  the  idea  of  these  green  rings 
enclosing  sheltered  harbors  and  quiet  lakes  in 
mid-ocean,  and  the  subject  has  lost  none  of  its 
fascination  since  the  mystery  of  their  existence 
has  been  solved  by  the  investigations  of  several 
contemporary  naturalists,  who  have  enabled  us  to 
trace  the  whole  story  of  their  structure.  I  would 
refer  all  who  wish  for  a  more  detailed  account 
of  them  to  Charles  Darwin's  charming  little  vol- 
ume on  "  Coral  Reefs,"  where  their  mode  of 
formation  is  fully  described,  and  also  to  James 
D.  Dana's  "  Geological  Eeport  of  the  United 
States  Exploring  Expedition." 

Coral  Reefs  are  found  only  in  tropical  regions : 
although  Polyps,  animals  of  the  same  class  as 
those  chiefly  instrumental  in  their  formation,  are 


FORMATION   OF   CORAL  REEFS.  155 

found  in  all  parts  of  the  globe,  yet  the  Reef- 
Building  Polyps  are  limited  to  the  Tropics.  We 
are  too  apt  to  forget  that  the  homes  of  animals 
are  as  definitely  limited  in  the  water  as  on  the 
land.  Indeed,  the  subject  of  the  geographical 
distribution  of  animals  according  to  laws  regu- 
lated by  altitude,  by  latitude  and  longitude,  by 
pressure  of  atmosphere  or  pressure  of  water,  by 
temperature,  light,  &c.,  already  alluded  to  in  a 
previous  article,  is  exceedingly  interesting,  and 
presents  a  most  important  field  of  investigation. 
The  climatic  effect  of  different  levels  of  al- 
titude upon  the  growth  of  animals  and  plants 
is  the  same  as  that  of  different  degrees  of  lati- 
tude ;  and  the  slope  of  a  high  mountain  in  the 
Tropics,  from  base  to  summit,  presents  in  a 
condensed  form,  an  epitome,  as  it  were,  of  the 
same  kind  of  gradation  in  vegetable  growth  that 
may  be  observed  from  the  Tropics  to  the  Arctics. 
At  the  base  of  such  a  mountain  we  have  all  the 
luxuriance  of  growth  characteristic  of  the  tropi- 
cal forest,  —  the  Palms,  the  Bananas,  the  Bread- 
trees,  the  Mimosas ;  higher  up,  these  give  way 
to  a  different  kind  of  growth,  corresponding  to 
our  Oaks,  Chestnuts,  Maples,  etc. ;  as  these  wane, 
on  the  loftier  slopes  comes  in  the  Pine  forest, 
fading  gradually,  as  it  ascends,  into  a  dwarfish 
growth  of  the  same  kind ;  and  this  at  last  gives 
way  to  the  low  creeping  Mosses  and  Lichens  of 


156       FOKMATION  OF  CORAL  REEFS. 

the  greater  heights,  till  even  these  find  a  foot- 
hold no  longer,  and  the  summit  of  the  moun- 
tain is  clothed  in  perpetual  snow  and  ice.  What 
have  we  here  but  the  same  series  of  changes 
through  which  we  pass,  if,  travelling  northward 
from  the  Tropics,  we  leave  Palms  and  Pome- 
granates and  Bananas  behind,  where  the  Live- 
Oaks  and  Cypresses,  the  Orange-trees  and  Myrtles 
of  the  warmer  Temperate  Zone  come  in,  and 
these  die  out  as  we  reach  the  Oaks,  Chestnuts, 
Maples,  Elms,  Nut-trees,  Beeches,  and  Birches 
of  the  colder  Temperate  Zone,  these  again  waning 
as  we  enter  the  Pine  forests  of  the  Arctic  bor- 
ders, till,  passing  out  of  these,  nothing  but  a 
dwarf  vegetation,  a  carpet  of  Moss  and  Lichen, 
fit  food  for  the  Reindeer  and  the  Esquimaux, 
greets  us,  and  beyond  that  lies  the  region  of 
the  snow  and  ice  fields,  impenetrable  to  all  but 
the  daring  Arctic  voyager? 

I  have  thus  far  spoken  of  the  changes  in  the  veg- 
etable growth  alone  as  influenced  by  altitude  and 
latitude,  but  the  same  is  equally  true  of  animals. 
Every  zone  of  the  earth's  surface  has  its  own 
animals,  suited  to  the  conditions  under  which 
they  are  meant  to  live  ;  and,  with  the  exception  of 
those  that  accompany  man  in  all  his  pilgrimages, 
and  are  subject  to  the  same  modifying  influences 
by  which  he  adapts  his  home  and  himself  to 
all  climates,  animals  are  absolutely  bound  by 


FORMATION  OF  COEAL  REEFS.       157 

the  laws  of  their  nature  within  the  range  assigned 
to  them.  Nor  is  this  the  case  only  on  land, 
where  river-banks,  lake  shores,  and  mountain- 
ranges  might  be  supposed  to  form  the  impassa- 
ble boundaries  that  keep  animals  within  certain 
limits ;  but  the  ocean,  as  well  as  the  land,  has  its 
faunae  and  florae  bound  within  their  respective 
zoological  and  botanical  provinces ;  and  a  wall  of 
granite  is  not  more  impassable  to  a  marine  ani- 
mal than  that  ocean-line,  fluid,  and  flowing,  and 
ever-changing  though  it  be,  on  which  is  written 
for  him,  "  Hitherto  shalt  thou  come,  but  no  far- 
ther." One  word  as  to  the  effect  of  pressure  on 
animals  will  explain  this. 

We  all  live  under  the  pressure  of  the  atmos- 
phere. Now,  thirty-two  feet  under  the  sea  dou- 
bles that  pressure,  since  a  column  of  water  of 
that  height  is  equal  in  weight  to  the  pressure 
of  one  atmosphere.  At  the  depth  of  thirty-two 
feet,  then,  any  marine  animal  is  under  the  press- 
ure of  two  atmospheres,  —  that  of  the  air,  which 
surrounds  our  globe,  and  of  a  weight  of  water 
equal  to  it ;  at  sixty-four  feet  he  is  under  the 
pressure  of  three  atmospheres,  and  so  on,  —  the 
weight  of  one  atmosphere  being  always  added 
for  every  thirty-two  feet  of  depth.  There  is  a 
great  difference  in  the  sensitiveness  of  animals  to 
this  pressure.  Some  fishes  live  at  a  great  depth, 
and  find  the  weight  of  water  genial  to  them ; 


158       FORMATION  OF  CORAL  REEFS. 

while  others  would  be  killed  at  once  by  the  same 
pressure ;  and  the  latter  naturally  seek  the  shal- 
low waters.  Every  fisherman  knows  that  he 
must  throw  a  long  line  for  a  Halibut,  while  with 
a  common  fishing-rod  he  will  catch  plenty  of 
Perch  from  the  rocks  near  the  shore ;  and  the 
differently  colored  bands  of  sea-weed  revealed 
by  low  tides,  from  the  green  line  of  the  Ulvas 
through  the  brown  zone  of  the  common  Fucus, 
to  the  rosy  and  purple-hued  sea-weeds  of  the 
deeper  water,  show  that  the  florae  as  well  as  the 
faunae  of  the  ocean  have  their  precise  boun- 
daries. 

.  This  wider  or  narrower  range  of  marine  ani- 
mals is  in  direct  relation  to  their  structure,  which 
enables  them  to  bear  a  greater  or  less  pressure  of 
water.  All  fishes,  and,  indeed,  all  animals  hav- 
ing a  wide  range  of  distribution  in  ocean-depths, 
have  a  special  apparatus  of  water-pores,  so  that 
the  surrounding  element  penetrates  their  struc- 
ture, thus  equalizing  the  pressure  of  the  weight, 
which  is  diminished  from  without  in  proportion 
to  the  quantity  of  water  they  can  admit  into  their 
bodies.  Marine  animals  differ  in  their  ability  to 
sustain  this  pressure,  just  as  land  animals  differ 
in  their  power  of  enduring  great  variations  of 
climate  and  of  atmospheric  pressure. 

Of  all  air-breathing  animals,  none  exhibits  a 
more  surprising  power  of  adapting  itself  to  great 


FORMATION  OF  CORAL  KEEFS.       159 

and  rapid  changes  of  external  influences  than  the 
Condor.  It  may  be  seen  feeding  on  the  sea-shore 
under  a  burning  tropical  sun,  and  then,  rising 
from  its  repast,  it  floats  up  among  the  highest 
summits  of  the  Andes,  and  is  lost  to  sight  beyond 
them,  miles  above  the  line  of  perpetual  snow, 
where  the  temperature  must  be  lower  than  that 
of  the  Arctics.  But  even  the  Condor,  sweeping 
at  one  flight  from  tropic  heat  to  arctic  cold, 
although  it  passes  through  greater  changes  of 
temperature,  does  not  undergo  such  changes  of 
pressure  as  a  fish  that  rises  from  a  depth  of  sixty- 
four  feet  to  the  surface  of  the  sea ;  for  the  former 
remains  within  the  air  that  surrounds  our  globe, 
and  therefore  the  increase  or  diminution  of  press- 
ure to  which  it  is  subjected  must  be  confined 
within  the  limits  of  one  atmosphere ;  while  the 
latter,  at  a  depth  of  sixty-four  feet,  is  under  a 
weight  equal  to  that  of  three  such  atmospheres, 
which  is  reduced  to  one  when  it  reaches  the  sea- 
level.  The  change  is  proportionally  greater  for 
those  fishes  that  come  from  a  depth  of  several 
hundred  feet.  These  laws  of  limitation  in  space 
explain  many  facts  in  the  growth  of  Coral  Reefs 
that  would  be  otherwise  inexplicable,  and  which  I 
now  will  endeavor  to  make  clear  to  my  readers. 

For  a  long  time  it  was  supposed  that  the  Reef- 
Builders  inhabited  very  deep  waters,  for  they  were 
sometimes  brought  up  on  sounding-lines  from  a 


160       FORMATION  OF  CORAL  REEFS. 

depth  of  many  hundreds,  or  even  thousands,  of 
feet,  and  it  was  taken  for  granted  that  they  must 
have  had  their  home  where  they  were  found ; 
but  the  facts  recently  ascertained  respecting  the 
subsidence  of  ocean-bottoms  have  shown  that  the 
foundation  of  a  Coral  wall  may  have  sunk  far 
below  the  place  where  it  was  laid.  And  it  is  now 
proved,  beyond  a  doubt,  that  no  Reef-Building 
Coral  can  thrive  at  a  depth  of  more  than  fifteen 
fathoms,  though  Corals  of  other  kinds  occur  far 
lower,  and  that  the  dead  Reef-Corals,  sometimes 
brought  to  the  surface  from  much  greater  depths, 
are  only  broken  fragments  of  some  Reef  that  has 
subsided  with  the  bottom  on  which  it  was  grow- 
ing. But  though  fifteen  fathoms  is  the  maximum 
depth  at  which  any  Reef-Builder  can  prosper, 
there  are  many  which  will  not  sustain  even  that 
degree  of  pressure  ;  and  this  fact  has,  as  we  shall 
see,  an  important  influence  on  the  structure  of 
the  Reef. 

Imagine  now  a  sloping  shore  on  some  tropical 
coast  descending  gradually  below  the  surface  of 
the  sea.  Upon  that  slope,  at  a  depth  of  from  ten 
to  twelve  or  fifteen  fathoms,  and  two  or  three  or 
more  miles  from  the  main  land,  according  to  the 
shelving  of  the  shore,  we  will  suppose  that  one  of 
those  little  Coral  animals,  to  whom  a  home  in 
such  deep  waters  is  genial,  has  established  itself. 
How  it  happens  that  such  a  being,  which  we 


FORMATION  OF   COKAL  REEFS.  161 

know  is  immovably  attached  to  the  ground,  and 
forms  the  foundation  of  a  solid  wall,  was  ever 
able  to  swim  freely  about  in  the  water  till  it 
found  a  suitable  resting-place,  I  shall  explain 
hereafter,  when  I  say  something  of  the  mode  of 
reproduction  of  these  animals.  Accept,  for  the 
moment,  my  unsustained  assertion,  and  plant 
our  little  Coral  on  this  sloping  shore,  some  twelve 
or  fifteen  fathoms  below  the  surface  of  the  sea. 

The  internal  structure  of  such  a  Coral  corre- 
sponds to  that  of  the  Sea- Anemone.  The  body  is 
divided  by  vertical  partitions  from  top  to  bottom, 
leaving  open  chambers  between;  while  in  the 
centre  hangs  the  digestive  cavity,  connected  by 
an  opening  in  the  bottom  with  all  these  cham- 
bers. At  the  top  is  an  aperture  serving  as  a 
mouth,  surrounded  by  a  wreath  of  hollow  tenta- 
cles, each  one  of  which  connects  at  its  base  with 
one  of  the  chambers,  so  that  all  parts  of  the  ani- 
mal communicate  freely  with  each  other.  But 
though  the  structure  of  the  Coral  is  identical  in 
all  its  parts  with  that  of  the  Sea-Anemone,  it 
nevertheless  presents  one  important  difference. 
The  body  of  the  Sea-Anemone  is  soft,  while 
that  of  the  Coral  is  hard. 

It  is  well  known  that  all  animals  and  plants 
have  the  power  of  appropriating  to  themselves 
and  assimilating  the  materials  they  need,  each 
selecting  from  the  surrounding  elements  whatever 


162       FORMATION  OF  CORAL  REEFS. 

contributes  to  its  well-being.  Now  Corals  possess, 
in  an  extraordinary  degree,  the  power  of  assimi- 
lating to  themselves  the  lime  contained  in  the  salt 
water  around  them ;  and  as  soon  as  our  little 
Coral  is  established  on  a  firm  foundation,  a  lime 
deposit  begins  to  form  in  all  the  walls  of  its  body, 
so  that  its  base,  its  partitions,  and  its  outer  wall, 
which  in  the  Sea- Anemone  remain  always  soft, 
become  perfectly  solid  in  the  Polyp  Coral,  and 
form  a  frame  as  hard  as  bone. 

It  may  naturally  be  asked  where  the  liine 
comes  from  in  the  sea  which  the  Corals  absorb  in 
such  quantities.  As  far  as  the  living  Corals  are 
concerned,  the  answer  is  easy,  for  an  immense 
deal  of  lime  is  brought  down  to  the  ocean  by 
rivers  that  wear  away  the  lime  deposits  through 
which  they  pass.  The  Mississippi,  whose  course 
lies  through  extensive  lime  regions,  brings  down 
yearly  lime  enough  to  supply  all  the  animals  liv- 
ing in  the  Gulf  of  Mexico.  But  behind  this  lies 
a  question  not  so  easily  settled,  as  to  the  origin  of 
the  extensive  deposits  of  limestone  found  at  the 
very  beginning  of  life  upon  earth.  This  problem 
brings  us  to  the  threshold  of  astronomy,  for  the 
base  ^of  limestone  is  metallic  in  character,  sus- 
ceptible therefore  of  fusion,  and  may  have  formed 
a  part  of  the  materials  of  our  earth,  even  in  an 
incandescent  state,  when  the  worlds  were  forming. 
But  though  this  investigation  as  to  the  origin  of 


FOKMATION  OF  COEAL  EEEFS.       163 

lime  does  not  belong  either  to  the  naturalist  or 
the  geologist,  its  suggestion  reminds  us  that  the 
time  has  come  when  all  the  sciences  and  their 
results  are  so  intimately  connected  that  no  one 
caii  be  carried  on  independently  of  the  others. 
Since  the  study  of  the  rocks  has  revealed  a 
crowded  life  whose  records  are  hoarded  within 
them,  the  work  of  the  geologist  and  the  natural- 
ist has  become  one  and  the  same,  and  at  that 
border-land  where  the  first  crust  of  the  earth  was 
condensed  out  of  the  igneous  mass  of  materials 
which  formed  its  earliest  condition,  their  investi- 
gation mingles  with  that  of  the  astronomer,  and 
we  cannot  trace  the  limestone  in  a  little  Coral 
without  going  -back  to  the  creation  of  our  solar 
system,  when  the  worlds  that  compose  it  were 
thrown  off  from  a  central  mass  in  a  gaseous 
condition. 

When  the  Coral  has  become  in  this  way  per- 
meated with  lime,  all  parts  of  the  body  are 
rigid,  with  the  exception  of  the  upper  margin, 
the  stomach,  and  the  tentacles.  The  tentacles 
are  soft  and  waving,  projected  or  drawn  in  at 
will ;  they  retain  their  flexible  character-  through 
life,  and  decompose  when  the  animal  dies.  For 
this  reason  the  dried  specimens  of  Corals  preserved 
in  museums  do  not  give  us  the  least  idea  of  the 
living  Corals,  in  which  every  one  of  the  millions 
of  beings  composing  such  a  community  is  crowned 


164       FORMATION  OF  CORAL  REEFS. 

by  a  waving  wreath  of  white  or  green  or  rose- 
colored  tentacles. 

As  soon  as  the  little  Coral  is  fairly  established 
and  solidly  attached  to  the  ground,  it  begins  to 
bud.  This  may  take  place  in  a  variety  of  ways, 
dividing  at  the  top  or  budding  from  the  base  or 
from  the  sides,  till  the  primitive  animal  is  sur- 
rounded by  a  number  of  individuals  like  itself, 
of  which  it  forms  the  nucleus,  and  which  now 
begin  to  bud  in  their  turn,  each  one  surrounding 
itself  with  a  numerous  progeny,  all  remaining, 
however,  attached  to  the  parent.  Such  a  com- 
munity increases  till  its  individuals  are  numbered 
by  millions ;  and  I  have  myself  counted  no  less 
than  fourteen  millions  of  individuals  in  a  Coral 
mass  of  Porites  measuring  not  more  than  twelve 
feet  in  diameter.  The  so-called  Coral  heads, 


which  make  the  foundation  of  a  Coral  wall,  and 
seem  by  their  massive  character  and  regular  form 


FORMATION  OF  CORAL  REEFS.       165 

especially  adapted  to  give  a  strong,  solid  base  to 
the  whole  structure,  are  known  in  our  classifica- 
tions as  the  Astrasans,  so  named  on  account  of 
the  star-shaped  form  of  the  little  pits  crowded 
upon  their  surface,  each  one  of  which  marks  the 
place  of  a  single  more  or  less  isolated  individual 
in  such  a  community. 

Thus  firmly  and  strongly  is  the  foundation  of 
the  reef  laid  by  the  Astraeans  ;  but  we  have  seen 
that  for  their  prosperous  growth  they  require  a 
certain  depth  and  pressure  of  water,  and  when 
they  have  brought  the  wall  so  high  that  they  have 
not  more  than  six  fathoms  of  water  above  them, 
this  kind  of  Coral  ceases  to  grow.  They  have, 
however,  prepared  a  fitting  surface  for  different 
kinds  of  Corals  that  could  not  live  in  the  depths 
from  which  the  Astraeans  have  come,  but  find 
their  genial  home  nearer  the  surface  ;  such  a 
home  being  made  ready  for  them  by  their  prede- 
cessors, they  now  establish  themselves  on  the  top 
of  the  Coral  wall  and  continue  its  growth  for  a 
certain  time.  These  are  the  Meandrinas,  or  the 
so-called  Brain-Corals,  and  the  Porites.  The  Me- 
andrinas differ  from  the  Astraeans  by  their  less 
compact  and  definite  pits.  In  the  Astraeans  the 
place  occupied  by  the  animal  in  the  community 
is  marked  by  a  little  star-shaped  spot,  in  the  cen- 
tre of  which  all  the  partition-walls  meet.  But  in 
the  Meandrinas,  although  all  the  partitions  con- 


166 


FORMATION   OF   CORAL   REEFS. 


verge  toward  the  central  opening,  as  in  the  As- 
traeaiis,  these  central  openings  elongate,  run  into 
each  other,  and  form  waving  furrows  all  over 
the  surface,  instead  of  the  small  round  pits  so 


characteristic  of  the  Astraeans.     The  Porites  re- 
semble the  Astraeans,  but  the   pits  are  smaller, 


with  fewer  partitions  and  fewer  tentacles,  and 
their  whole  substance  is  more  porous. 


FORMATION  OF  CORAL  REEFS.       167 

But  these  also  have  their  bounds  within  the 


sea:  they  in  their  turn  reach  the  limit  beyond 
which  they  are  forbidden  by  the  laws  of  their  na- 


ture to  pass,  and  there  they  also  pause.     But  the 


168  FORMATION   OF   COEAL   REEFS. 

Coral  wall  continues  its  steady  progress ;  for 
here  the  lighter  kinds  set  in,  —  the  Madrepores 
(p.  167),  the  Millepores,  and  a  great  variety  of 
Sea-Fans  (p.  167,  below)  and  Corallines,  and  the 
reef  is  crowned  at  last  with  a  many-colored 
shrubbery  of  low  feathery  growth.  These  are 
all  branching  in  form,  and  many  of  them  are 
simple  calciferous  plants,  though  most  of  them 
are  true  animals,  resembling,  however,  delicate 
Alga3  more  than  any  marine  animals ;  but,  on 
examination  of  the  latter,  one  finds  them  to  be 
covered  with  myriads  of  minute  dots,  each  repre- 
senting one  of  the  little  beings  out  of  which 
the  whole  is  built,  while  nothing  of  the  kind 
is  seen  in  Algae. 

I  would  add  here  one  word  on  the  true  nature 
of  the  Millepores.  long  misunderstood  by  natu- 


ralists, because  this  type  throws  light  not  only  on 
some  interesting  facts  respecting  Coral  Reefs,  es- 
pecially the  ancient  ones,  but  also  because  it  tells 
us  something  of  the  early  inhabitants  of  the  globe, 
and  shows  us  that  a  class  of  Radiates  supposed 
to  be  missing  in  the  primitive  creation  had  its 
representatives  then  as  now. 


FORMATION  OF  CORAL  REEFS.       169 

In  the  diagram  of  the  geological  periods  intro- 
duced in  a  previous  article,  I  have  represented  all 
the  three  classes  of  Radiates,  Polyps,  Acalephs, 
and  Echinoderms  as  present  on  the  first  floor  of 
our  globe  which  was  inhabited  at  all.  But  it  is 
only  recently  that  positive  proofs  have  been  found 
of  the  existence  of  Acalephs  or  Jelly-Fishes,  as 
they  are  called,  at  that  early  period.  Their  very 
name  indicates  their  delicate  structure  ;  and  were 
there  no  remains  preserved  in  the  rocks  of  these 
soft,  transparent  creatures,  it  would  yet  be  no 
evidence  that  they  did  not  exist.  Fragile  as  they 
are,  however,  they  have  left  here  and  there  some 
faint  record  of  themselves,  and  in  the  Museum 
at  Carlsruhe,  on  a  slab  from  Solenhofen,  I  have 
seen  a  very  perfect  outline  of  one  which  remains 
undescribed  to  this  day.  This,  however,  does 
not  carry  them  farther  back  than  the  Jurassic 
period,  and  it  is  only  lately  that  I  have  satisfied 
myself  that  they  not  only  existed,  but  were 
among  the  most  numerous  animals  in  the  first 
representation  of  organic  life. 

The  earliest  Corals  correspond  in  certain  fea- 
tures of  their  structure  to  the  Millepores*.  They 
differ  from  them  as  all  early  animals  differ  from 
the  succeeding  ones,  every  geological  period  hav- 
ing its  special  set  of  representatives.  But  still 
they  are  always  true  to  their  class,  and  have  a 
certain  general  correspondence  with  animals  of 

8 


170  FORMATION   OF   CORAL   REEFS. 

like  kind  that  follow  them  in  later  periods.  In 
this  sense  the  Millepores  are  in  our  epoch  the 
representatives  of  those  early  Corals,  called  by 
naturalists  Tabulata  and  Rugosa,  —  distinguished 
from  the  Polyp  Corals  by  the  horizontal  floors, 
waving  in  some,  straight  in  others,  which  di- 
vide the  body  transversely  at  successive  heights 
through  its  whole  length,  and  also  by  the  absence 
of  the  vertical  partitions,  extending  from  top  to 
bottom  of  each  animal,  so  characteristic  of  the 
true  Polyps. 

Notwithstanding  these  differences,  they  were 
for  a  long  time  supposed  to  be  Polyps,  and  I  had 
shared  in  this  opinion,  till,  during  the  winter  of 
1857,  while  pursuing  my  investigations  on  the 
Coral  Reefs  of  Florida,  one  of  these  Millepores 
revealed  itself  to  me  in  its  true  character  of  Aca- 
leph.  It  must  be  remembered  that  they  belong 
to  the  Hydroid  group  of  Acalephs,  of  which  our 
common  jelly-fishes  do  not  give  a  correct  idea- 
it  is  by  their  soft  parts  alone  —  those  parts  which 
are  seen  only  when  these  animals  are  alive  and 
fully  open  —  that  their  Acalephian  character 
can  be  perceived,  and  this  accounts  for  their 
being  so  long  accepted,  as  Polyps,  when  studied 
in  the  dry  Coral  stock.  Nothing  could  exceed 
my  astonishment  when  for  the  first  time  I  saw 
such  an  animal  fully  expanded,  and  found  it  to 
be  a  true  Acaleph.  It  is  exceedingly  difficult  to 


FORMATION  OF  CORAL  REEFS.       171 

obtain  a  view  of  them  in  this  state,  for,  at  any 
approach,  they  draw  themselves  in,  and  remain 
closed  to  all  investigation.  Only  once,  for  a 
short  hour,  I  had  this  opportunity ;  during  that 
time  one  of  these  little  creatures  revealed  to  me 
its  whole  structure,  as  if  to  tell  me,  once  for  all, 
the  story  of  its  existence  through  all  the  succes- 
sive epochs  from  the  dawn  of  Creation  till  now, 
and  then  withdrew.  With  my  most  patient 
watching,  I  have  never  been  able  to  see  one  of 
them  open  again.  But  to  establish  the  fact  that 
one  of  the  Corals  represented  from  the  earliest 
period,  and  indeed  far  more  numerous  in  the 
beginning  than  any  other,  was  in  truth  no 
Polyp,  but  an  Acaleph,  the  glimpse  I  had  was 
all-sufficient.  It  came  out  as  if  to  bear  witness 
of  its  class,  —  as  if  to  say,  "  We,  too,  were 
among  the  hosts  of  living  beings  with  which 
God  first  peopled  his  earth." 

With  these  branching  Corals  the  reef  reaches 
the  level  of  high-water,  beyond  which,  as  I  have 
said,  there  can  be  no  further  growth,  for  want  of 
the  action  of  the  fresh  sea-water.  This  depend- 
ence upon  the  vivifying  influence  of  the  sea  ac- 
counts for  one  unfailing  feature  in  the  Coral 
walls.  They  are  always  abrupt  and  steep  on  the 
seaward  side,  but  have  a  gentle  slope  towards  the 
land.  This  is  accounted  for  by  the  circum- 
stance that  the  Corals  on  the  outer  side  of  the 


172       FOBMATION  OF  CORAL  REEFS. 

reef  are  in  immediate  contact  with  the  pure 
ocean-water,  while  by  their  growth  they  partially 
exclude  the  inner  ones  from  the  same  influence, 
—  the  rapid  growth  of  the  latter  being  also  im- 
peded by  any  impurity  or  foreign  material  washed 
away  from  the  neighboring  shore  and  mingling 
with  the  water  that  fills  the  channel  between  the 
main-land  and  the  reef.  Thus  the  Coral  Reefs, 
whether  built  around  an  island,  or  along  a  straight 
line  of  coast,  or  concentric  to  a  rounding  shore, 
are  always  shelving  toward  the  land,  while  they 
are  comparatively  abrupt  and  steep  toward  the 
sea.  This  should  be  remembered,  for,  as  we 
shall  see  hereafter,  it  has  an  important  bearing 
on  the  question  of  time  as  illustrated  by  Coral 
Reefs. 

I  have  spoken  of  the  budding  of  Corals,  by 
which  each  one  becomes  the  centre  of  a  cluster ; 
but  this  is  not  the  only  way  in  which  they  multi- 
ply their  kind.  They  give  birth  to  eggs  also, 
which  are  carried  on  the  inner  edge  of  their  par- 
tition-walls, till  they  drop  into  the  sea,  where 
they  float  about,  little,  soft,  transparent,  pear* 
shaped  bodies,  as  unlike  as  possible  to  the  rigid 
stony  structure  they  are  to  assume  hereafter. 
In  this  condition  they  are  covered  with  vibratile 
cilia  or  fringes,  that  are  always  in  rapid,  unin- 
terrupted motion,  and  by  means  of  which  they 
swim  about  in  the  water.  These  little  germs  of 


FORMATION  OF  CORAL  REEFS.       173 

the  Corals,  swimming  freely  about  during  their 
earliest  phases  of  life,  continue  the  growth  of 
the  reef,  those  that  prosper  at  shallower  depths 
coming  in  at  the  various  heights  where  their  pre- 
decessors die  out ;  otherwise  it  would  be  impossi- 
ble to  understand  how  this  variety  of  building 
material,  as  it  were,  is  introduced  wherever  it 
is  needed.  This  point,  formerly  a  puzzle  to 
naturalists,  has  become  quite  clear  since  it  has 
been  found  that  myriads  of  these  little  germs 
are  poured  into  the  water  surrounding  a  reef. 
There  they  swim  about  till  they  find  a  genial 
spot  on  which  to  establish  themselves,  when  they 
become  attached  to  the  ground  by  one  end,  while 
a  depression  takes  place  at  the  opposite  end, 
which  gradually  deepens  to  form  the  mouth  and 
inner  cavity,  while  the  edges  expand  to  form 
the  tentacles,  and  the  productive  life  of  the  little 
Coral  begins :  it  buds  from  every  side,  and  be- 
comes the  foundation  of  a  new  community. 

I  should  add,  that,  beside  the  Polyps  and  the 
Acalephs,  Mollusks  also  have  their  representa- 
tives among  the  Corals.  There  is  a  group  of 
small  Mollusks  called  Bryozoa,  allied  to  the  Clams 
by  their  structure,  but  excessively  minute  when 
compared  to  the  other  members  of  their  class, 
which,  like  the  other  Corals,  harden  in  conse- 
quence of  an  absorption  of  solid  materials,  and 
contribute  to  the  formation  of  the  reef.  Besides 


174       FORMATION  OF  CORAL  REEFS. 

these,  there  are  certain  plants,  limestone  Algae, 
—  Corallines,  as  they  are  called,  —  which  have 
their  share  also  in  the  work. 

I  had  intended  to  give  some  account  of  the 
Coral  Reefs  of  Florida,  and  to  show  what  bear- 
ing they  have  upon  the  question  of  time  and 
the  permanence  of  Species ;  but  this  cursory 
sketch  of  Coral  Reefs  in  general  has  grown  to 
such  dimensions  that  I  must  reserve  a  more 
particular  account  of  the  Florida  Reefs  and  Keys 
for  a  future  article. 


AGE   OF   CORAL  REEFS.  175 


CHAPTER    XII. 

AGE   OF   CORAL  REEFS  AS   SHOWING  PERMANENCE  OF 
SPECIES. 

A  FEW  miles  from  the  southern  extremity  of 
Florida,  separated  from  it  by  a  channel,  narrow 
at  the  eastern  end,  but  widening  gradually  to- 
ward the  west,  and  rendered  every  year  more 
and  more  shallow  by  the  accumulation  of  mate- 
rials constantly  collecting  within  it,  there  lies  a 
line  of  islands  called  the  Florida  Keys.  They 
are  at  different  distances  from  the  shore,  stretch- 
ing gradually  seaward  in  the  form  of  an  open 
crescent,  from  Virginia  Key  and  Key  Biscayne, 
almost  adjoining  the  main-land,  to  Key  West,  at 
a  distance  of  twelve  miles  from  the  coast,  which 
does  not,  however,  close  the  series,  for  sixty  miles 
farther  west  stands  the  group  of  the  Tortugas, 
isolated  in  the  Gulf  of  Mexico.  Thotfgh  they 
seem  disconnected,  these  islands  are  parts  of  a 
submerged  Coral  Reef,  parallel  with  the  shore  of 
the  peninsula  and  continuous  underneath  the 
water,  but  visible  above  the  surface  at  such  points 
of  the  summit  as  have  fully  completed  their 
growth. 


176 


AGE  OF   CORAL  REEFS. 


This  demands  some  explanation,  since  I  have 
already  said  that  no  Coral  growth  can  continue 
after  it  has  reached  the  line  of  high  water.  But 


we  have  not  finished  the  history  of  a  Coral  wall, 
when  we  have  followed  it  to  the  surface  of  the 
ocean.  It  is  true  that  its  normal  growth  ceases 
there,  but  already  a  process  of  partial  decay  has 
begun  that  insures  its  further  increase.  Here, 
as  elsewhere,  destruction  and  construction  go 
hand  in  hand,  and  the  materials  broken  or 


AGE   OF   COKAL  REEFS.  177 

worn  away  from  one  part  of  the  Reef  help  to 
build  it  up  elsewhere.  The  Corals  forming  the 
Reef  are  not  the  only  beings  that  find  their  home 
there  :  many  other  animals  —  Shells,  Worms, 
Crabs,  Star-Fishes,  Sea-Urchins  —  establish  them- 
selves upon  it,  work  their  way  into  its  interstices, 
and  seek  a  shelter  in  every  little  hole  and  cranny 
made  by  the  irregularities  of  its  surface.  In  the 
Zoological  Museum  at  Cambridge  there  are  some 
large  fragments  of  Coral  Reef  which  give  one  a 
good  idea  of  the  populous  aspect  that  such  a 
Reef  would  present,  could  we  see  it  as  it  actually 
exists  beneath  the  water.  Some  of  these  frag- 
ments consist  of  a  succession  of  terraces,  as  it 
were,  in  which  are  many  little  miniature  caves, 
where  may  still  be  seen  the  Shells  or  Sea-Urchins 
which  made  their  snug  and  sheltered  homes  in 
these  recesses  of  the  Reef. 

We  must  not  consider  the  Reef  as  a  solid,  mas- 
sive structure  throughout.  The  compact  kinds  of 
Corals,  giving  strength  and  solidity  to  the  wall, 
may  be  compared  to  the  larger  trees  in  a  forest, 
giving  it  shade  and  density ;  but  beneath  these 
larger  trees  grow  all  kinds  of  trailing  vines, 
ferns,  and  mosses,  wild-flowers,  and  low  shrubs, 
filling  the  spaces  between  them  with  a  thick  un- 
derbrush. The  Coral  Reef  also  has  its  under- 
brush of  the  lighter,  branching,  more  brittle 
kinds,  filling  its  interstices,  and  fringing  the  sum- 

8*  L 


178  AGE   OF   CORAL   REEFS. 

mit  and  the  sides  with  their  delicate,  graceful 
forms.  Such  an  intricate  underbrush  of  Coral 
growth  affords  an  excellent  retreat  for  many 
animals  that  like  its  protection  better  than  ex- 
posure to  the  open  sea,  just  as  many  land-animals 
prefer1  the  close  and  shaded  woods  to  the  open 
plain.  A  forest  is  not  more  thickly  peopled  with 
Birds,  Squirrels,  Martens,  and  the  like,  than  is 
the  Coral  Reef  with  a  variety  of  animals  which 
do  not  contribute  in  any  way  to  its  growthf  but 
find  shelter  in  its  crevices,  or  in  its  near  neigh- 
borhood. 

But  these  larger  animals  are  not  the  only  ones 
that  haunt  the  forest.  There  is  a  host  of  parasites 
besides,  principally  Insects  and  their  larvae,  which 
bore  their  way  into  the  very  heart  of  the  tree, 
making  their  home  in  the  bark  and  pith,  and  not 
the  less  numerous  because  hidden  from  sight. 
These  also  have  their  counterparts  in  the  Reef, 
where  numbers  of  boring  Shells  and  marine 
Worms  work  their  way  into  the  solid  substance 
of  the  wall,  piercing  it  with  holes  in  every  direc- 
tion, till  large  portions  become  insecure,  and  the 
next  storm  suffices  to  break  off  the  fragments  so 
loosened.  Once  detached,  they  are  tossed  about 
in  the  water,  crumbled  into  Coral  sand,  crushed, 
often  ground  to  powder  by  the  friction  of  the 
rocks  and  the  constant  action  of  the  sea. 

After   a   time,  an  immense  quantity  of  such 


AGE   OF   CORAL   REEFS.  179 

materials  is  formed  about  a  Coral  Reef.  Tides 
and  storms  constantly  throw  them  up  on  its  sur- 
face, and  at  last  a  soil  collects  on  the  top  of  the 
Reef,  wherever  it  has  reached  the  surface  of  the 
water,  formed  chiefly  of  its  own  d£bris,  of  Coral 
sand,  Coral  fragments,  even  large  masses  of  Coral 
rock,  mingled  with  the  remains  of  the  animals 
that  have  had  their  home  about  the  Reef,  with 
sea-weeds,  with  mud  from  the  neighboring  land, 
and  with  the  thousand  loose  substances  always 
floating  about  in  the  vicinity  of  a  coast,  and 
thrown  upon  the  rocks  or  shore  with  every  wave 
that  breaks  against  them.  Add  to  this  the  pres- 
ence of  a  lime-cement  in  the  water,  resulting 
from  the  decomposition  of  some  of  these  mate- 
rials, and  we  have  all  that  is  needed  to  make  a 
very  compact  deposit  and  fertile  soil,  on  which  a 
vegetation  may  spring  up,  whenever  seeds  float- 
ing from  the  shore,  or  dropped  by  birds  in  their 
flight,  take  root  on  the  newly  formed  island. 

There  is  one  plant  belonging  to  tropical  or  sub- 
tropical climates  that  is  peculiarly  adapted  by  its 
mode  of  growth  to  the  soil  of  these  islands,  and 
contributes  greatly  to  their  increase.  This  is  the 
Mangrove-tree.  Its  seeds  germinate  in  the  calyx 
of  the  flower,  and,  before  they  drop,  grow  to  bo 
little  brown  stems,  some  six  or  seven  inches  long, 
and  about  as  thick  as  a  finger,  with  little  rootlets 
at  one  end.  Such  Mangrove-seedlings,  looking 


180  AGE   OF   CORAL   REEFS. 

more  like  cigars  than  anything  else,  float  in  large 
numbers  about  the  Reef.  I  have  sometimes  seen 
them  in  the  water  about  the  Florida  Reef  in  such 
quantities,  that  one  would  have  said  some  vessel 
laden  with  Havana  cigars  had  been  wrecked 
there,  and  its  precious  cargo  scattered  in  the 
ocean. 

In  consequence  of  their  shape,  and  the  devel- 
opment of  the  root,  one  end  is  a  little  heavier 
than  the  other,  so  that  they  float  unevenly,  with 
the  loaded  end  a  little  lower  than  the  lighter  one. 
When  they  are  brought  by  the  tide  against  such 
a  cap  of  soil  as  I  have  described,  they  become 
stranded  upon  it  by  their  heavier  end ;  the  root- 
lets attach  themselves  slightly  to  the  soil ;  the 
advancing  and  retreating  waves  move  the  little 
plant  up  and  down,  till  it  works  a  hole  in  the 
sand ;  and  having  thus  established  itself  more 
firmly,  steadied  itself,  as  it  were,  it  now  stands 
upright ;  and,  as  it  grows,  throws  out  numerous 
roots,  even  from  a  height  of  several  feet  above 
the  ground,  till  it  lias  surrounded  the  lower  part 
of  its  stem  with  a  close  net-work  of  roots.  Against 
this  natural  trellis,  or  screen,  all  sorts  of  mate- 
rials collect.  Sand,  mud,  and  shells  are  caught 
in  it.  And  as  these  Man  grove- trees  grow  in  large 
numbers,  and  to  the  height  of  thirty  feet,  they 
contribute  greatly  to  the  solidity  and  compact- 
ness of  the  shores  on  which  they  are  stranded. 


AGE   OF   CORAL  REEFS.  181 

Such  caps  of  soil  on  the  summit  of  a  Coral 
Reef  are  of  course  very  insecure,  till  they  are 
consolidated  by  a  long  period  of  accumulation, 
and  they  may  even  be  swept  completely  away  by 
a  violent  storm.  It  is  not  many  years  since  the 
light-house,  built  on  Sand  Key  for  the  greater 
security  of  navigation  along  the  Reef,  was  swept 
away,  with  the  whole  island  on  which  it  stood. 
Thanks  to  the  admirably  conducted  investigations 
of  the  Coast-Survey,  this  part  of  our  seaboard, 
formerly  so  dangerous  on  account  of  the  Coral 
Reefs,  is  now  better  understood,  and  every  pre- 
caution has  been  taken  to  insure  the  safety  of 
vessels  sailing  along  the  coast  of  Florida. 

I  cannot  deny  myself  the  pleasure  of  paying  a 
tribute  here  to  the  high  scientific  character  of  the 
distinguished  superintendent  of  this  survey,  who 
has  known  so  well  how  to  combine  the  most  im- 
portant scientific  aims  with  the  most  valuable 
practical  results  in  his  direction  of  it.  If  some 
have  hitherto  doubted  the  practical  value  of  such 
researches,  —  and  unhappily  there  are  always 
those  who  estimate  intellectual  efforts  only  by 
their  material  results,  —  one  would  t^ink  that 
these  doubts  must  be  satisfied,  now  that  the 
Coast-Survey  is  seen  to  be  the  right  arm  of  our 
navy.  Most  of  the  leaders  in  our  late  naval  ex- 
peditions have  been  men  trained  in  its  service, 
and  familiar  with  all  the  harbors,  with  every 


182  AGE   OF   CORAL  REEFS. 

bay  and  inlet  of  our  Southern  coasts,  from  hav- 
ing been  engaged  in  the  extensive  researches 
undertaken  by  Dr.  Bache,  and  carried  out  under 
his  guidance.  Many  even  of  the  pilots  of  our 
Southern  fleets  are  men  who  have  been  employed 
upon  this  work,  and  owe  their  knowledge  of  the 
coast  to  their  former  occupation.  It  is  a  singular 
fact,  that  at  this  very  time,  when  the  whole  coun- 
try feels  its  obligation  to  the  men  who  have 
devoted  so  many  years  of  their  lives  to  these 
investigations,  a  proposition  should  have  been 
brought  forward  in  Congress  for  the  suspension 
of  the  Coast-Survey  on  economical  grounds. 
Happily,  the  almost  unanimous  rejection  of  this 
proposition  has  shown  the  appreciation  in  which 
the  work  is  held  by  our  national  legislature. 
Even  without  reference  to  their  practical  useful- 
ness, it  is  a  sad  sign,  when,  in  the  hour  of  her 
distress,  a  nation  sacrifices  first  her  intellectual 
institutions.  Then,  more  than  ever,  when  she 
needs  all  the  culture,  all  the  wisdom,  all  the 
comprehensiveness  of  her  best  intellects,  should 
she  foster  the  institutions  that  have  fostered 
them,  and  in  which  they  have  been  trained  to  do 
good  service  to  their  country  in  her  time  of  need. 
Several  of  the  Florida  Keys,  such  as  Key 
West  and  Indian  Key,  are  already  large,  inhabited 
islands,  several  miles  in  extent.  The  interval 
between  them  and  the  main-land  is  gradually 


AGE   OF   CORAL   REEFS.  183 

filling  up,  by  a  process  similar  to  that  by  which 
the  islands  themselves  were  formed.  The  gentle 
landward  slope  of  the  Reef  and  the  channel  be- 
tween it  and  the  shore,  are  covered  with  a  growth 
of  the  more  branching  lighter  Corals,  such  as  Sea- 
Fans,  Corallines,  etc.,  answering  the  same  pur- 
pose as  the  intricate  roots  of  the  Mangrove-tree. 
All  the  debris  of  the  Reef,  as  well  as  the  sand 
and  mud  washed  from  the  shore,  collect  in  this 
net-work  of  Coral  growth  within  the  channel, 
and  soon  transform  it  into  a  continuous  mass, 
with  a  certain  degree  of  consistence  and  solidity. 
This  forms  the  foundation  of  the  mud-flats  which 
are  now  rapidly  filling  the  channel,  and  must 
eventually  connect  the  Keys  of  Florida  with  the 
present  shore  of  the  peninsula. 

Outside  the  Keys,  but  not  separated  from  them 
by  so  great  a  distance  as  that  which  intervenes 
between  them  and  the  main-land,  there  stretches 
beneath  the  water  another  Reef,  abrupt,  like  the 
first,  on  its  seaward  side,  but  sloping  gently  to- 
ward the  inner  Reef,  and  divided  from  it  by  a 
channel.  This  outer  Reef  and  channel  are,  how- 
ever, in  a  much  less  advanced  state  than  the 
preceding  ones.  Only  here  and  there  a  sand-flat 
large  enough  to  afford  a  foundation  for  a  bea- 
con, or  a  light-house,  shows  that  this  Reef  also 
is  gradually  coming  to  the  surface,  and  that  a 
series  of  islands  corresponding  to  the  Keys  must 
eventually  be  formed  upoii  its  summit. 


184  AGE   OF  CORAL  REEFS. 

Some  of  my  readers  may  ask  why  the  Reef 
does  not  rise  evenly  to  the  level  of  the  sea,  and 
form  a  continuous  line  of  land,  instead  of  here 
and  there  an  island.  This  is  accounted  for  by 
the  sensitiveness  of  the  Corals  to  any  unfavorable 
circumstances  impeding  their  growth,  as  well  as 
by  the  different  rates  of  increase  of  their  differ- 
ent kinds.  Wherever  any  current  from  the  shore 
flows  over  the  Reef,  bringing  with  it  impurities 
from  the  land,  there  the  growth  of  the  Corals 
will  be  less  rapid,  and  consequently  that  portion 
of  the  Reef  will  not  reach  the  surface  so  soon 
as  other  parts,  where  no  such  unfavorable  influ- 
ences have  interrupted  the  growth.  But  in  the 
course  of  time  the  outer  Reef  will  reach  the 
surface  for  its  whole  length,  and  become  united 
to  the  inner  one  by  the  filling  up  of  the  channel 
between  them,  while  the  inner  one  will  long 
before  that  time  become  solidly  united  to  the 
present  shore-bluffs  of  Florida  by  the  consolida- 
tion of  the  mud-flats,  which  will  one  day  trans- 
form the  inner  channel  'into  dry  land. 

What  is  now  the  rate  of  growth  of  these  Coral 
Reefs  ?  We  cannot,  perhaps,  estimate  it  with 
absolute  accuracy,  since  they  are  now  so  nearly 
completed  ;  but  Coral  growth  is  constantly  spring- 
ing up  wherever  it  can  find  a  foothold,  and  it 
is  not  difficult  to  ascertain  approximately  the 
rate  of  growth  of  the  different  kinds.  Even  this, 


AGE   OF   CORAL  REEFS.  185 

however,  would  give  us  far  too  high  a  standard ; 
for  the  rise  of  the  Coral  Reef  is  not  in  propor- 
tion to  the  height  of  the  living  Corals,  but  to 
their  solid  parts  which  never  decompose.  Add 
to  this  that  there  are  many  brittle,  delicate  kinds 
that  have  a  considerable  height  when  alive,  but 
contribute  to  the  increase  of  the  Reef  only  so 
much  additional  thickness  as  their  branches 
would  have  if  broken  and  crushed  down  upon 
its  surface.  A  forest  in  its  decay  does  not  add  to 
the  soil  of  the  earth  a  thickness  corresponding 
to  the  height  of  its  trees,  but  only  such  a  thin 
layer  as -would  be  left  by  the  decomposition  of 
its  whole  vegetation.  In  the  Coral  Reef,  also, 
we  must  allow  not  only  for  the  deduction  of  the 
soft  parts,  but  also  for  the  comminution  of  all 
these  little  branches,  which  would  be  broken 
and  crushed  by  the  action  of  the  storms  and 
tides,  and  add,  therefore,  but  little  to  the  Reef 
in  proportion  to  their  size  when  alive. 

The  foundations  of  Fort  Jefferson,  which  is 
built  entirely  of  Coral  rock,  were  laid  on  the 
Tortugas  Islands  in  the  year  1846.  A  very  in- 
telligent head-workman  watched  the  growth  of 
certain  Corals  that  established  themselves  on 
these  foundations,  and  recorded  their  rate  of 
increase.  He  has  shown  me  the  rocks  on  which 
Corals  had  been  growing  for  some  dozen  years, 
during  which  they  had  increased  at  the  rate  of 


186  AGE   OF   CORAL  REEFS. 

about  half  an  inch  in  ten  years.  I  have  col- 
lected facts  from  a  variety  of  sources  and  local- 
ities that  confirm  this  testimony.  A  brick  placed 
under  water,  in  the  year  1850,  by  Captain  Wood- 
bury  of  Tortugas,  with  the  view  of  determining 
the  rate  of  growth  of  Corals,  when  taken  up 
in  1858  had  a  crust  of  Mseandrina  upon  it  a  little 
more  than  half  an  inch  in  thickness.  Mr.  Allen 
also  sent  me  from  Key  West  a  number  of  frag- 
ments of  Masandrina  from  the  breakwater  at 
Fort  Taylor  ;  they  had  been  growing  from  twelve 
to  fifteen  years,  and  have  an  average  thickness 
of  about  an  inch.  The  specimens  vary  in  this 
respect,  —  some  of  them  being  a  little  more  than 
an  inch  in  thickness,  others  not  more  than  half 
an  inch.  Fragments  of  Oculina  gathered  at  the 
same  place  and  of  the  same  age  are  from  one 
to  three  inches  in  height  and  width ;  but  these 
belong  to  the  lighter,  more  branching  kinds  of 
corals,  which,  as  we  have  seen,  cannot,  from  their 
brittle  character,  be  supposed  to  add  their  whole 
height  to  the  solid  mass'of  the  Coral  wall.  Mille- 
pore  gives  a  similar  result. 

Estimating  the  growth  of  the  Coral  Keef  ac- 
cording to  these  and  other  data  of  the  same 
character,  it  should  be  about  half  a  foot  in  a 
century  ;  and  a  careful  comparison  which  I  have 
made  of  the  condition  of  the  Reef  as  recorded 
in  an  English  survey  made  about  a  century  ago 


AGE    OF    CORAL   REEFS.  187 

with  its  present  state  would  justify  this  conclu- 
sion. But,  allowing  a  wide  margin  for  inaccu- 
racy of  observation  or  for  any  circumstances  that 
might  accelerate  the  growth,  and  leaving  out  of 
consideration  the  decay  of  the  soft  parts  and  the 
comminution  of  the  brittle  ones,  which  would 
subtract  so  largely  from  the  actual  rate  of  growth, 
let  us  double  this  estimate  and  call  the  average 
increase  a  foot  for  every  century.  In  so  doing, 
we  are  no  doubt  greatly  overrating  the  rapidity 
of  the  progress,  and  our  calculation  of  the  period 
that  must  have  elapsed  in  the  formation  of  the 
Reef  will  be  far  within  the  truth. 

The  outer  Reef,  still  incomplete,  as  I  have 
stated,  and  therefore  of  course  somewhat  lower 
than  the  inner  one,  measures  about  seventy  feet 
in  height.  Allowing  a  foot  of  growth  for  every 
century,  not  less  than  seven  thousand  years  must 
have  elapsed  since  this  Reef  began  to  grow. 
Some  miles  nearer  the  main-land  are  the  Keys, 
or  the  inner  Reef;  and  though  this  must  have 
been  longer  in  the  process  of  formation  than  the 
outer  one,  since  its  growth  is  completed,  and 
nearly  the  whole  extent  of  its  surface  is  trans- 
formed into  islands,  with  here  and  there  a  nar- 
row break  separating  them,  yet,  in  order  to  keep 
fully  within  the  evidence  of  the  facts,  I  will  allow 
only  seven  thousand  years  for  the  formation  of 
this  Reef  also,  making  fourteen  thousand  for 
the  two. 


188  AGE   OF   COKAL   REEFS. 

This  brings  us  to  the  shore-bluffs,  consisting 
simply  of  another  Reef  exactly  like  those  already 
described,  except  that  in  course  of  time  it  has  been 
united  to  the  main-land  by  the  complete  filling  up 
and  consolidation  of  the  channel  which  once  di- 
vided it  from  the  extremity  of  the  peninsula,  as 
a  channel  now  separates  the  Keys  from  the  shorc- 
bluffs,  and  the  outer  Beef,  again,  from  the  Keys. 
These  three  concentric  Reefs,  then,  the  outer 
Reef,  the  Keys,  and  the  shore-bluffs,  if  we  meas- 
ure the  growth  of  the  two  latter  on  the  same 
low  estimate  by  which  I  have  calculated  the  rate 
of  progress  of  the  former,  cannot  have  reached 
their  present  condition  in  less  than  twenty  thou- 
sand years.  Their  growth  must  have  been  suc- 
cessive, since,  as  we  have  seen,  all  Corals  need 
the  fresh  action  of  the  open  sea  upon  them,  and 
if  either  of  the  outer  Reefs  had  begun  to  grow 
before  the  completion  of  the  inner  one,  it  would 
have  effectually  checked  the  growth  of  the  latter. 
The  absence  of  an  incipient  Reef  outside  of  the 
outer  Reef  shows  these  conclusions  to  be  well 
founded.  The  islands  capping  these  three  reefs 
do  not  exceed  in  height  the  level  to  which  the 
fragments  accumulated  upon  their  summits  may 
have  been  thrown  by  the  heaviest  storms.  The 
highest  hills  of  this  part  of  Florida  are  not  over 
ten  or  twelve  feet  above  the  level  of  the  sea, 
and  yet  the  luxuriant  vegetation  with  which  they 


AGE   OF   CORAL   REEFS.  189 

are  covered  gives  them  an  imposing  appear- 
ance, recalling  the  islands  of  the  Pacific. 

But  this  is  not  the  end  of  the  story.  Travel- 
ling inland  from  the  shore-bluffs,  we  cross  a  low, 
flat  expanse  of  land,  the  Indian  hunting-ground, 
which  brings  us  to  a  row  of  elevations  called 
the  Hummocks.  This  hunting-ground,  or  Ever- 
glade as  it  is  also  called,  is  an  old  channel, 
changed  first  to  mud-flats  and  then  to  dry  land 
by  the  same  kind  of  accumulation  that  is  filling 
up  the  present  channels,  and  the  row  of  hum- 
mocks is  but  an  old  Coral  Reef  with  the  Keys 
or  islands  of  past  days  upon  its  summit.  Seven 
such  Eeefs  and  channels  of  former  times  have 
already  been  traced  between  the  shore-bluffs  and 
Lake  Okee-cho-bee,  adding  some  fifty  thousand 
years  to  our  previous  estimate.  Indeed,  upon 
the  lowest  calculation,  based  upon  the  facts  thus 
far  ascertained  as  to  their  growth,  we  cannot 
suppose  that  less  than  seventy  thousand  years 
have  elapsed  since  the  Coral  Reefs  already  known 
to  exist  in  Florida  began  to  grow. 

When  we  remember  that  this  is  but  a  small 
portion  of  the  peninsula,  and  that,  though  we 
have  no  very  accurate  information  as  to  the 
nature  of  its  interior,  yet  the  facts  already  ascer- 
tained in  the  northern  part  of  the  State,  formed, 
like  its  southern  extremity,  of  Coral  growth,  justify 
the  inference  that  the  whole  peninsula  is  formed 


190  AGE   OF   CORAL   REEFS. 

of  successive  concentric  Reefs,  we  must  believe 
that  hundreds  of  thousands  of  years  have  elapsed 
since  its  formation  began.  Leaving  aside,  how- 
ever, all  that  part  of  its  history  which  is  not 
susceptible  of  positive  demonstration  in  the  pres- 
ent state  of  our  knowledge,  I  will  limit  my  re- 
sults to  the  evidence  of  facts  already  within  our 
possession  ;  and  these  give  us  as  the  lowest  pos- 
sible estimate  a  period  of  seventy  thousand  years 
for  the  formation  of  that  part  of  the  peninsula 
which  extends  south  of  Lake  Okee-cho-bee  to  the 
present  outer  Reef. 

So  much  for  the  duration  of  the  Reefs  them- 
selves. What,  now,  do  they  tell  us  of  the  per- 
manence of  the  Species  by  which  they  were 
formed  ?  In  these  seventy  thousand  years  has 
there  been  any  change  in  the  Corals  living  in  the 
Gulf  of  Mexico  ?  I  answer  most  emphatically, 
No.  Astraeans,  Porites,  Maeandrinas,  and  Mad- 
repores were  represented  by  exactly  the  same 
Species  seventy  thousand  years  ago  as  they  are 
now.  Were  we  to  classify  the  Florida  Corals 
from  the  Reefs  of  the  interior,  the  result  would 
correspond  exactly  to  a  classification  founded 
upon  the  living  Corals  of  the  outer  Reef  to-day. 
There  would  be  among  the  Astraeans  the  differ- 
ent Species  of  Astraea  proper,  forming  the  close 
round  heads,  —  the  Mussa,  growing  in  smaller 
stocks,  where  the  mouths  coalesce  and  run  into 


AGE   OF   CORAL   REEFS.  191 

each  other  as  in  the  Brain-Corals,  but  in  which  the 
depression  formed  by  the  mouths  are  deeper,  — 
and  the  Caryophyllians,  in  which  the  single  in- 
dividuals stand  out  more  distinctly  from  the 
stock  ;  among  Porites-,  the  P.  Astrseoides,  with 
pits  resembling  those  of  the  Astrseans  in  form, 
though  smaller  in  size,  and  growing  also  in  solid 
heads,  though  these  masses  are  covered  with 
club-shaped  protrusions,  instead  of  presenting  a 
smooth,  even  surface  like  the  Astraeans,  —  and 
the  P.  Clavaria,  in  which  the  stocks  are  divided 
in  short,  stumpy  branches,  with  club-shaped  ends, 
instead  of  growing  in  close,  compact  heads  ; 
among  the  Maeandrinas  we  should  have  the 
round  heads  we  know  as  Brain-Corals,  with  their 
wavy  lines  over  the  surface,  and  the  Manicina, 
differing  again  from  the  preceding  by  certain  de- 
tails of  structure  ;  among  the  Madrepodes  we 
should  have  the  Madrepora  prolifera,  with  its 
small,  short  branches,  broken  up  by  very  frequent 
ramifications,  the  M.  cervicornis,  with  longer 
and  stouter  branches  and  less  frequent  ramifica- 
tions, arid  the  cup-like  M.  palmata,  resembling 
an  open  sponge  in  form.  Every  Species,  in 
short,  that  lives  upon  the  present  Reef  is  found 
in  the  more  ancient  ones.  They  all  belong  to 
our  own  geological  period,  and  we  cannot,  upon 
the  evidence  before  us,  estimate  its  duration  at 
less  than  seventy  thousand  years,  during  which 


192  AGE   OF   CORAL  EEEFS. 

time  we  have  no  evidence  of  any  change  in 
Species,  but,  on  the  contrary,  the  strongest  proof 
of  the  absolute  permanence  of  those  Species 
whose  past  history  we  have  been  able  to  trace. 

Before  leaving  the  subject  of  the  Coral  Reefs, 
I  would  add  a  few  words  on  the  succession  of  the 
different  kinds  of  Polyp  Corals  on  a  Reef  as  com- 
pared with  their  structural  rank  and  also  with 
their  succession  in  time,  because  we  have  here 
another  of  those  correspondences  of  thought, 
those  intellectual  links  in  Creation,  which  give 
such  coherence  and  consistency  to  the  whole, 
and  make  it  intelligible  to  man. 

The  lowest  in  structure  among  the  Polyps  are 
not  Corals,  but  the  single,  soft-bodied  Actiniae. 
They  have  no  solid  parts,  and  are  independent 
in  their  mode  of  existence,  never  forming  com- 
munities, like  the  higher  members  of  the  class. 
It  might  at  first  seem  strange  that  independence, 
considered  a  sign  of  superiority  in  the  higher 
animals,  should  here  be  looked  upon  as  a  mark 
of  inferiority.  But  independence  may  mean 
either  simple  isolation,  or  independence  of  ac- 
tion ;  and  the  life  of  a  single  Polyp  is  no  more 
independent  in  the  sense  of  action  than  that  of 
a  community  of  Polyps.  It  is  simply  not  con- 
nected with  or  related  to  the  life  of  any  others. 
The  mode  of  development  of  these  animals  tells 
us  something  of  the  relative  inferiority  and  su- 


AGE  OF  COBAL  REEFS.  193 

periority  of  the  single  ones  and  of  those  that 
grow  in  communities.  When  the  little  Polyp 
Coral,  the  Astrasan  or  Madrepore,  for  instance,  is 
born  from  the  egg,  it  is  as  free  as  the  Actinia, 
which  remains  free  all  its  life.  It  is  only  at  a 
later  period,  as  its  development  goes  on,  that  it 
becomes  solidly  attached  to  the  ground,  and  be- 
gins its  compound  life  by  putting  forth  new 
beings  like  itself  as  buds  from  its  side.  Since 
we  cannot  suppose  that  the  normal  development 
of  any  being  can  have  a  retrograde  action,  we 
are  justified  in  believing  that  the  loss  of  freedom 
is  in  fact  a  stage  of  progress  in  these  lower 
animals,  and  their  more  intimate  dependence  on 
each  other  a  sign  of  maturity. 

There  are,  however,  structural  features  by 
which  the  relative  superiority  of  these  animals 
may  be  determined.  In  proportion  as  the  num- 
ber of  their  parts  is  limited  and  permanent,  their 
structure  is  more  complicated  ;  and  the  indefi- 
nite multiplication  of  identical  parts  is  connected 
with  inferiority  of  structure.  Now  in  these  low- 
est Polyps,  the  Actiniae,  the  tentacles  increase 
with  age  indefinitely,  never  ceasing  to  grow  while 
life  lasts,  new  chambers  being  constantly  added 
to  correspond  with  them,  till  it  becomes  impossi- 
ble to  count  their  numbers.  Next  to  these  come 
the  true  Fungidae.  They  are  also  single,  and, 
though  they  are  stony  Corals,  they  have  no  share 


194  AGE   OF   CORAL  REEFS. 

in  the  formation  of  Reefs.  In  these,  also,  the 
tentacles  multiply  throughout  life,  though  they 
are  usually  not  so  numerous  as  in  the  Actiniae. 
But  a  new  feature  is  added  to  the  complication 
of  their  structure,  as  compared  with  Actiniae,  in 
the  transverse  beams  which  connect  their  vertical 
partitions,  though  they  do  not  stretch  across  the 
chambers  so  as  to  form  perfect  floors,  as  in  some 
of  the  higher  Polyps.  These  transverse  beams  or 
floors  must  not  be  confounded  with  the  horizon- 
tal floors  alluded  to  in  a  former  article  as  char- 
acteristic of  the  ancient  Acalephian  Corals,  the 
Rugosa  and  Tabulata.  For  in  the  latter  these 
floors  stretch  completely  across  the  body,  unin- 
terrupted by  vertical  partitions,  which,  if  they 
exist  at  all,  pass  only  from  floor  to  floor,  instead 
of  extending  unbroken  through  the  whole  height 
of  the  body,  as  in  all  Polyps.  Where,  on  the 
contrary,  transverse  floors  exist  in  true  Polyps, 
they  never  cut  the  vertical  partitions  in  their 
length,  but  simply  connect  their  walls,  stretching 
wholly  or  partially  from  wall  to  wall. 

In  the  Astraeans,  the  multiplication  of  tenta- 
cles is  more  definite  and  limited,  rising  some- 
times to  ninety  and  more,  though  often  limited  to 
forty-eight  in  number,  and  the  transverse  floors 
between  the  vertical  partitions  are  more  com- 
plete than  in  the  Fungidas.  The  Porites  have 
twelve  tentacles  only,  never  more  and  never  less, 


AGE   OF   CORAL  KEEFS.  195 

and  in  them  the  whole  solid  frame  presents  a 
complicated  system  of  connected  beams.  The 
Madrepores  have  also  twelve  tentacles,  but  they 
have  a  more  definite  character  than  those  of  the 
Porites,  on  account  of  their  regular  alternation 
in  six  smaller  and  six  larger  ones  ;  in  these  also 
the  transverse  floors  are  perfect,  but  exceedingly 
delicate.  Another  remarkable  feature  among  the 
Madrepores  consists  in  the  prominence  of  one  of 
the  Polyps  on  the  summit  of  the  branches,  show- 
ing a  kind  of  subordination  of  the  whole  com- 
munity to  these  larger  individuals,  and  thus  sus- 
taining the  view  expressed  above,  that  the  com- 
bination of  many  individuals  into  a  connected 
community  is  among  the  Polyps  a  character  of 
superiority  when  contrasted  with  the  isolation 
of  the  Actiniae.  In  the  Sea-Fans,  the  Halcyo- 
noids,  as  they  are  called  in  our  classification, 
the  number  of  tentacles  is  always  eight,  four 
of  which  are  already  present  at  the  time  of 
their  birth,  arranged  in  pairs,  while  the  other 
four  are  added  later.  Their  tentacles  are  lobed 
all  around  the  margin,  and  are  much  more  com- 
plicated in  structure  than  those  of  the  preceding 
Polyps. 

According  to  the  relative  complication  of  their 
structure,  these  animals  are  classified  in  the 
following  order  :  — 


196  AGE   OF   CORAL  KEEFS. 

STRUCTURAL  SERIES. 

HALCYONOIDS:  eight  tentacles  in  pairs,  lobed  around  the  margin; 
always  combined  in  large  communities,  some  of  which  are  free 
and  movable  like  single  animals. 

MADREPORES:  twelve  tentacles,  alternating  in  six  larger  and  six 
smaller  ones;  frequently  a  larger  top  animal  standing  prominent 
in  the  whole  community,  or  on  the  summit  of  its  branches. 

PORITES  :  twelve  tentacles,  not  alternating  in  size ;  system  of  con- 
nected beams. 

ASTRAEANS  :  tentacles  not  definitely  limited  in  number,  though  usu- 
ally not  exceeding  one  hundred,  and  generally  much  below  this 
number;  transverse  floors.  Mseandrinas,  generally  referred  to 
Astraeans,  are  higher  than  the  true  Astraeans,  on  account  of  their 
compound  Polyps. 

FUKGID^;:  indefinite  multiplication  of  tentacles;  imperfect  trans- 
verse beams. 

ACTINIAE:  indefinite  multiplication  of  tentacles;  soft  bodies  and  no 
transverse  beams. 

If  now  we  compare  this  structural  gradation 
among  Polyps  with  their  geological  succession, 
we  shall  find  that  they  correspond  exactly.  The 
following  table  gives  the  geological  order  in 
which  they  have  been  introduced  upon  the  sur- 
face of  the  earth. 

GEOLOGICAL,  SUCCESSION. 

Present,  Halcyonoids. 

Pliocene,  "| 

Miocene,  f  Madrepores. 

Eocene, 

Cretaceous,  ^ 

Jurassic,  I    Porites 

Triassic,  and 

T,       .  Astraeans. 

Permian,  J 

Carboniferous,  "j 
Devonian,          r  Fungidae. 
Silurian, 


AGE   OF   CORAL   REEFS.  197 

With  regard  to  the  geological  position  of  the 
Actiniae  we  can  say  nothing,  because,  if  their  soft, 
gelatinous  bodies  have  left  any  impressions  in 
the  rocks,  none  such  have  ever  been  found  ;  but 
their  absence  is  no  proof  that  they  did  not  exist, 
since  it  is  exceedingly  improbable  that  animals 
destitute  of  any  hard  parts  could  be  preserved. 

The  position  of  the  Corals  on  a  Reef  accords 
with  these  series  of  structural  gradation  and  ge- 
ological succession.  It  is  true  that  we  do  not 

SUCCESSION  ON  THE   REEF. 
Halcyonoids. 


Astrseans. 


find  the  Actiniae  in  the  Reef  any  more  than  in  the 
crust  of  the  earth,  for  the  absence  of  hard  parts  in 
their  bodies  makes  them  quite  unfit  to  serve  as 
Reef-Builders.  Neither  do  we  find  Fungidae,  for 
they,  like  all  low  forms,  are  single,  and  not  con- 
fined to  one  level,  having  a  wider  range  in  depth 


198  AGE   OF   CORAL   REEFS. 

and  extent  than  other  stony  Polyps.  But  the 
true  Reef-Building  Polyps  follow  each  other  on 
the  Reef  in  the  same  order  as  prevails  in  their 
structural  gradation  and  their  geological  succes- 
sion ;  and  whether  we  classify  them  according  to 
their  position  on  the  Reef,  or  their  introduction 
upon  the  earth  in  the  course  of  time,  or  their 
relative  rank,  the  result  is  the  same. 

It  would  require  an  amount  of  details  that 
would  be  tedious  to  many  of  my  readers,  were  I 
to  add  here  the  evidence  now  on  record  proving 
that  the  embryological  development  of  these  ani- 
mals, so  far  as  it  is  known,  and  their  geographical 
distribution  over  the  whole  surface  of  our  globe, 
show  the  same  correspondence  with  the  other 
three  series.  But  this  recurrence  of  the  same 
thought  in  the  history  of  animals  of  the  same 
Type,  showing  that,  from  whatever  side  we  con- 
sider them,  their  creation  and  existence  seem  to 
be  guided  by  one  Mind,  is  so  important  in  the 
study  of  Nature,  that  I  shall  constantly  refer  to  it 
in  the  course  of  these  papers,  even  though  I  may 
sometimes  be  accused  of  unnecessary  repetition, 
or  of  extending  my  conclusions  beyond  the  facts. 

What  is  the  significance  of  these  coincidences  ? 
They  were  not  sought  for  by  the  different  inves- 
tigators, who  have  worked  quite  independently 
while  ascertaining  all  these  facts,  without  even, 
knowing  that  there  was  any  relation  between 


AGE   OF   CORAL  REEFS.  199 

them.  The  succession  of  fossil  Corals  has  been 
found  in  the  rocks  by  the  geologist,  —  the  embry- 
ologist  has  followed  the  changes  in  the  growth 
of  the  living  Corals,  —  the  zoologist  has  traced 
the  geographical  distribution  and  the  structural 
relations  of  the  full-grown  animals ;  but  it  is 
only  after  the  results  of  their  separate  investi- 
gations are  collected  and  compared  that  the 
coincidence  is  perceived,  and  all  find  that  they 
have  been  working  unconsciously  to  one  end. 
These  thoughts  in  Nature,  which  we  are  too  prone 
to  call  simply  facts,  when  in  reality  they  are  the 
ideal  conception  antecedent  to  the  very  existence 
of  all  created  beings,  are  expressed  in  the  objects 
of  our  study.  It  is  not  the  zoologist  who  invents 
the  structural  relations  establishing  a  gradation 
between  all  Polyps,  —  it  is  not  the  geologist  who 
places  them  in  the  succession  in  which  he  finds 
them  in  the  rocks,  —  it  is  not  the  embryologist 
who  devises  the  changes  through  which  the  living 
Polyps  pass  as  he  watches  their  growth ;  these 
investigators  only  read  what  they  see,  and,  when 
they  compare  their  results,  it  is  found  that  they 
all  tell  the  same  story.  He  who  reads  most  cor- 
rectly from  the  original  is  the  best  naturalist. 
What  unites  all  their  investigations,  and  makes 
them  perfectly  coherent  with  each  other,  is  the 
coincidence  of  thought  expressed  in  the  facts 
themselves.  In  other  words,  it  is  the  working 


200  AGE   OF   CORAL   REEFS. 

of  the  same   Intellect  through  all  time,  every- 
where. 

When  we  observe  the  practical  results  of  this 
sequence  in  the  position  of  Corals  on  the  reef, 
we  cannot  fail  to  see  that  it  is  not  a  mere  acci- 
dental difference  of  structure  and  relation,  but 
that  it  bears  direct  reference  to  the  part  these 
little  beings  were  to  play  in  Creation.  It  places 
the  solid  part  of  the  structure  at  the  base  of  the 
Reef.  —  it  fills  in  the  interstices  with  a  lighter 
growth,  —  it  crowns  the  summit  with  the  more 
delicate  kinds,  that  yield  to  the  action  of  the  tides 
and  are  easily  crushed  into  the  fine  sand  that 
forms  the  soil,  —  it  makes  a  masonry  solid, 
compact,  time-defying,  such  a  masonry  as  was 
needed  by  the  great  Architect,  who  meant  that 
these  smallest  creatures  of  His  hand  should  help 
to  build  His  islands  and  His  continents. 


HOMOLOGIES.  201 


CHAPTER    XIII. 

HOMOLOGIES. 

IT  may  seem  to  some  of  my  readers  that  1 
have  wandered  from  my  subject  and  forgotten 
the  title  of  these  articles,  which  purport  to  be  a 
series  of  papers  on  "  Methods  of  Study  in  Natu- 
ral History."  But  some  idea  of  the  progress  of 
Natural  History,  of  its  growth  as  a  science,  of 
the  gradual  evolving  of  general  principles  out  of 
a  chaotic  mass  of  facts,  is  a  better  aid  to  the  stu- 
dent than  direct  instruction  upon  special  modes 
of  investigation  ;  and  it  is  with  the  intention  of 
presenting  the  study  of  Natural  History  from 
this  point  of  view  that  I  have  chosen  my  title. 

I  have  endeavored  thus  far  to  show  how  scien- 
tific facts  have  been  systematized  so  as  to  form  a 
classification  that  daily  grows  more  true  to  Na- 
ture, in  proportion  as  its  errors  are  corrected  by 
a  more  intimate  acquaintance  with  the  facts ;  but 
I  will  now  attempt  a  more  difficult  task,  and  try 
to  give  some  idea  of  the  mental  process  by  which 
facts  are  transformed  into  scientific  truth.  I  fear 
that  the  subject  may  seem  very  dry  to  my  read- 

9* 


202  HOMOLOGIES. 

ers,  and  I  would  again  ask  their  indulgence  for 
details  absolutely  essential  to  my  purpose,  but 
which  would  indeed  be  very  wearisome,  did  they 
not  lead  us  up  to  an  intelligent  and  most  signifi- 
cant interpretation  of  their  meaning. 

I  should  be  glad  to  contribute  my  share  to- 
wards removing  the  idea  that  science  is  the  mere 
amassing  of  facts.  It  is  true  that  scientific  results 
grow  out  of  facts,  but  not  till  they  have  been  fer- 
tilized by  thought.  The  facts  must  be  collected, 
but  their  mere  accumulation  will  never  advance 
the  sum  of  human  knowledge  by  one  step ;  it  is 
the  comparison  of  facts  and  their  transformation 
into  ideas  that  lead  to  a  deeper  insight  into  the 
significance  of  Nature.  Stringing  words  together 
in  incoherent  succession  does  not  make  an  intelli- 
gible sentence  ;  facts  are  the  words  of  God,  and  we 
may  heap  them  together  endlessly,  but  they  will 
teach  us  little  or  nothing  till  we  place  them  in 
their  true  relations,  and  recognize  the  thought 
that  binds  them  together  as  a  consistent  whole. 

I  have  spoken  of  'the  plans  that  lie  at  the 
foundation  of  all  the  variety  of  the  Animal 
Kingdom  as  so  many  structural  ideas  which 
must  have  had  an  intellectual  existence  in  the 
Creative  Conception  independently  of  any  special 
material  expression  of  them.  Difficult  though 
it  be  to  present  these  plans  as  pure  abstract 
formulae,  distinct  from  the  animals  that  represent 


HOMOLOGIES.  203 

them,  I  would  nevertheless  attempt  to  do  it,  in 
order  to  show  how  the  countless  forms  of  animal 
life  have  been  generalized  into  the  few  grand, 
but  simple  intellectual  conceptions  on  which  all 
the  past  populations  of  the  earth  as  well  as  the 
present  creation  are  founded.  In  such  attempts 
to  divest  the  thought  of  its  material  expression, 
especially  when  that  expression  is  multiplied  in 
such  thousand-fold  variety  of  form  and  color,  our 
familiarity  with  living  animals  is  almost  an  obsta- 
cle to  our  success.  For  I  shall  hardly  be  able  to 
allude  to  the  formula  of  the  Radiates,  for  in- 
stance, —  the  abstract  idea  that  includes  all  the 
structural  possibilities  of  that  division  of  the  An- 
imal Kingdom,  —  without  recalling  to  my  read- 
ers a  Polyp  or  a  Jelly-Fish,  a  Sea-Urchin  or  a 
Star-Fish.  Neither  can  I  present  the  structural 
elements  of  the  Mollusk  plan,  without  reminding 
them  of  an  Oyster  or  a  Clam,  a  Snail  or  a  Cuttle- 
Fish, —  or  of  the  Articulate  plan,  without  calling 
up  at  once  the  form  of  a  Worm,  a  Lobster,  or  an 
Insect,  —  or  of  the  Vertebrate  plan,  without 
giving  it  the  special  character  of  Fish,  Reptile, 
Bird,  or  Mammal.  Yet  I  insist  that  all  living 
beings  are  but  the  different  modes  of  expressing 
these  formulae,  and  that  all  animals  have,  within 
the  limits  of  their  own  branch  of  the  Animal 
Kingdom,  the  same  structural  elements,  though 
each  branch  is  entirely  distinct.  If  this  be  true, 


204  HOMOLOGIES. 

and  if  these  organic  formulae  have  the  precision 
of  mathematical  formulae,  with  which  I  have 
compared  them,  they  should  be  susceptible  of  the 
same  tests. 

The  mathematician  proves  the  identity  of  prop- 
ositions that  have  the  same  mathematical  value 
and  significance  by  their  convertibility.  If  they 
have  the  same  mathematical  quantities,  it  must 
be  possible  to  transform  them,  one  into  another, 
without  changing  anything  that  is  essential  in 
either.  The  problem  before  us  is  of  the  same 
character.  If,  for  instance,  all  Radiates,  be  they 
Sea- Anemones,  Jelly-Fishes,  Star-Fishes,  or  Sea- 
Urchins,  are  only  various  modes  of  expressing 
the  same  organic  formula,  each  having  the  sum 
of  all  its  structural  elements,  it  should  be  possi- 
ble to  demonstrate  that  they  are  reciprocally  con- 
vertible. This  is  actually  the  case,  and  I  hope  to 
be  able  to  convince  my  readers  that  it  is  no  fanci- 
ful theory,  but  may  be  demonstrated  as  clearly  as 
the  problems  of  the  geometer.  The  naturalist 
has  his  mathematics,  as  well  as  the  geometer  and 
the  astronomer ;  and  if  the  mathematics  of  the  An- 
imal Kingdom  have  a  greater  flexibility  than  those 
of  the  positive  sciences,  and  are  therefore  not  so 
easily  resolved  into  their  invariable  elements,  it 
is  because  they  have  the  freedom  and  pliability  of 
life,  and  evade  our  efforts  to  bring  all  their  exter- 
nal variety  within  the  limits  of  the  same  structu- 


HOMOLOGIES.  205 

ral  law  which  nevertheless  controls  and  includes 
them  all. 

I  wish  that  I  could  take  as  the  illustration  of 
this  statement  animals  with  whose  structure  the 
least  scientific  of  my  readers  might  be  presumed 
to  be  familiar ;  but  such  a  comparison  of  the 
Vertebrates,  showing  the  identity  and  relation  of 
structural  elements  throughout  the  Branch,  or 
even  in  any  one  of  its  Classes,  would  be  too  ex- 
tensive and  complicated,  and  I  must  resort  to  the 
Radiates,  —  that  branch  of  the  Animal  Kingdom 
which,  though  less  generally  known,  has  the  sim- 
plest structural  elements. 

I  will  take,  then,  for  the  further  illustration  of 
my  subject,  the  Radiates,  and  especially  the  class 
of  Echinoderms,  Star-Fishes,  Sea-Urchins,  and 
the  like,  both  in  the  fossil  and  the  living  types ; 
and  though  some  special  description  of  these  ani- 
mals is  absolutely  essential,  I  will  beg  my  readers 
to  remember  that  the  general  idea,  and  not  its 
special  manifestations,  is  the  thing  I  am  aiming 
at,  and  that,  if  we  analyze  the  special  parts  char- 
acteristic of  these  different  groups,  it  is  only  that 
we  may  resolve  them  back  again  into  the  struc- 
tural plan  that  includes  them  all. 

I  have  already  in  a  previous  article  named  the 
different  Orders  of  this  Class  in  their  relative 
rank,  and  have  compared  the  standing  of  the  liv- 
ing ones,  according  to  the  greater  or  less  compli- 


206  HOMOLOGIES. 

cation  of  their  structure,  with  the  succession  of 
the  fossil  ones.  Of  the  five  Orders,  Beches-de-Mer, 
Sea-Urchins,  Star-Fishes,  Ophiurans,  and  Cri- 
noids,  —  or,  to  name  them  all  according  to  their 
scientific  nomenclature,  Holothurians,  Echinoids, 
Asterioids,  Ophiurans,  and  Crinoids,  —  the  last- 
named  are  lowest  in  structure  and  earliest  in 
time.  Cuvier  was  the  first  naturalist  who  de- 
tected the  true  nature  of  the  Crinoids,  and 
placed  them  where  they  belong  in  the  classifica- 
tion of  the  Animal  Kingdom.  They  had  been 
observed  before,  and  long  and  laborious  investi- 
gations had  been  undertaken  upon  them,  but 
they  were  especially  baffling  to  the  student,  be- 
cause they  were  known  only  in  the  fossil  condi- 
tion from  incomplete  specimens ;  and  though 
they  still  have  their  representatives  among  the 
type  of  Echinoderms  as  it  exists  at  present,  yet, 
partly  owing  to  the  rarity  of  the  living  specimens 
and  partly  to  the  imperfect  condition  of  the  fossil 
ones,  the  relation  between  them  was  not  recog- 
nized. The  errors  about  them  certainly  did  not 
arise  from  any  want  of  interest  in  the  subject 
among  naturalists,  for  no  less  than  three  hundred 
and  eighty  authors  have  published  their  investi- 
gations upon  the  Crinoids,  and  the  books  that 
have  been  printed  about  these  animals,  many  of 
which  were  written  long  before  their  animal  na- 
ture was  suspected,  would  furnish  a  library  in 
themselves. 


HOMOLOGIES.  207 

The  ancients  knew  little  about  them.  The  only 
one  to  be  found  in  the  European  seas  resembles 
the  free  Star-Fishes  closely,  and  is  now  called 
Comatula  ;  but  even  Aristotle  was  ignorant  of  its 
true  structural  relations,  and  alludes  only  to  its 
motion  and  general  appearance.  Some  account 
of  the  gradual  steps  by  which  naturalists  have 
deciphered  the  true  nature  of  these  lowest  Echi- 
noderms  and  their  history  in  past  times  may  not 
be  without  interest,  and  is  very  instructive  as 
showing  how  such  problems  may  be  solved. 

In  the  sixteenth  century  some  stones  were 
found  bearing  the  impression  of  a  star  on  their 
surface.  They  received  the  name  of  Trochites, 
and  gave  rise  to  much  discussion.  Naturalists 
puzzled  their  brains  about  them,  called  them  star- 
shaped  crystals,  aquatic  plants,  corals ;  and  to 
these  last  Linnaeus  himself,  the  great  authority  of 
the  time  on  all  such  questions,  referred  them. 
Beside  these  stony  stars,  which  were  found  in 
great  quantities  when  attention  was  once  called 
to  them,  impressions  of  a  peculiar  kind  had  been 
observed  in  the  rocks,  resembling  flowers  on  long 
stems,  and  called  astone  lilies"  naturally  enough, 
for  their  long,  graceful  stems,  terminating  either 
in  a  branching  crown  or  a  closer  cup,  recall  the 
lily  tribe  among  flowers.  The  long  stems  of  these 
seeming  lilies  are  divided  transversely  at  regular 
intervals ;  the  stem  is  easily  broken  at  any  of 


208  HOMOLOGIES. 

these  natural  divisions,  and  on  each  such  frag- 
ment is  stamped  a  star-like  impression  resem- 
bling those  found  upon  the  loose  stones  or  Tro- 
chites. 

About  a  century  ago,  Guettard  the  naturalist 
described  a  curious  specimen  from  Porto  Rico,  so 
similar  to  these  fossil  lilies  of  the  rocks  that  he 
believed  they  must  have  some  relation  to  each 
other.  He  did  not  detect  its  animal  nature,  but 
from  its  long  stem  and  branching  crown  he 
called  it  a  marine  palm.  Thus  far  neither  the 
true  nature  of  the  living  specimen,  nor  of  the 
Trochites,  nor  of  the  fossil  lilies  was  understood, 
but  it  was  nevertheless  an  important  step  to  have 
found  that  there  was  a  relation  between  them. 
A  century  passed  away,  and  Guettard's  speci- 
men, preserved  at  the  Jardin  des  Plantes,  waited 
with  Sphinx-like  patience  for  the  man  who  should 
solve  its  riddle. 

Cuvier,  who  held  the  key  to  so  many  of  the 
secrets  of  Nature,  detected  at  last  its  true  struc- 
ture ;  he  pronounced  it  to  be  a  Star-Fish  with  a 
stem,  and  at  once  the  three  series  of  facts  respect- 
ing the  Trochites,  the  fossil  lilies,  and  Guettard's 
marine  palm  assumed  their  true  relation  to  each 
other.  The  Trochites  were  recognized  as  simply 
the  broken  portions  of  the  stem  of  some  of  these 
old  fossil  Crinoids,  and  the  Crinoids  themselves 
were  seen  to  be  the  ancient  representatives  of 


HOMOLOGIES.  209 

the  present  Comatulae  and  Star-Fishes  with  stems. 
So  is  it  often  with  the  study  of  Nature ;  many 
scattered  links  are  collected  before  the  man  comes 
who  sees  the  connection  between  them  and 
speaks  the  word  that  reconstructs  the  broken 
chain. 

I  will  begin  my  comparison  of  all  Echinoderms 
with  an  analysis  of  the  Star-Fishes  and  Sea- 
Urchins,  because  I  think  I  can  best  show  the 
identity  of  parts  between  them,  notwithstanding 
the  difference  in  their  external  form ;  the  Sea- 
Urchins  having  always  a  spherical  body,  while 
the  Star-Fishes  are  always  star-shaped,  though  in 
some  the  star  is  only  hinted  at,  sketched  out,  as 
it  were,  in  a  simply  pentagonal  outline,  while  in 
others  the  indentations  between  the  rays  are  very 
deep,  and  the  rays  themselves  so  intricate  in  their 
ramifications  as  to  be  broken  up  into  a  complete 
net-work  of  branches.  But  under  all  this  vari- 
ety of  outline,  our  problem  remains  always  the 
same :  to  build  with  the  same  number  of  pieces 
a  star  and  a  sphere,  having  the  liberty,  however, 
of  cutting  the  pieces  differently  and  changing 
their  relative  proportions.  Let  us  take  first  the 
Sea-Urchin  and  examine  in  detail  all  parts  of  its 
external  structure.  I  shall  say  nothing  of  the 
internal  structure  of  any  of  these  animals,  be- 
cause it  does  not  affect  the  comparison  of  their 
different  forms  and  the  external  arrangement 


210  HOMOLOGIES. 

of  parts,  which  is  the   subject  of  the   present 
article. 

On  the  lower  side  is  the  mouth,  and  we  may 
call  that  side  and  all  the  parts  radiating  from  it 
the  oral  region.  On  the  upper  side  is  a  small 
area  to  which  the  parts  converge,  and  which, 
from  its  position  just  opposite  the  so-called  mouth 
or  oral  opening,  we  may  call  the  ab-oral  region. 
I  prefer  these  more  general  terms,  because,  if  we 
speak  of  the  mouth,  we  are  at  once  reminded  of 
the  mouth  in  the  higher  animals,  and  in  this 
sense  the  word,  as  applied  to  the  aperture  through 
which  the  Sea-Ur chins  receive  their  food,  is  a 
misnomer.  Very  naturally  the  habit  has  become 
prevalent  of  naming  the  different  parts  of  ani- 
mals from  their  function,  and  not  from  their 
structure ;  and  in  all  animals  the  aperture 
through  which  food  enters  the  body  is  called  the 
mouth,  though  there  is  not  the  least  structural 
relation  between  the  organs  so  designated,  except 
within  the  limits  of  each  different  branch  or  di- 
vision. To  speak  of  these  opposite  regions  in  the 
Sea-Urchin  as  the  upper  and  lower  sides  would 
equally  mislead  us,  since,  as  we  have  seen,  there 
is,  properly  speaking,  no  above  and  below,  no  right 
and  left  sides,  no  front  and  hind  extremities  in 
these  animals,  all  parts  being  evenly  distributed 
around  a  vertical  axis.  I  will  therefore,  although 
it  has  been  my  wish  to  avoid  technicalities  as 


HOMOLOGIES.  211 

much  as  possible  in  these  papers,  make  use  of 
the  unfamiliar  terms  oral  and  ab-oral  regions,  to 
indicate  the  mouth  with  the  parts  diverging 
from  it  and  the  opposite  area  towards  which  all 
these  parts  converge.* 


Sea-Urchin  seen  from  the  oral  side,  showing  the  zones  with  the  spines  and 
the  suckers  ;  for  the  ab-oral  side,  on  the  summit  of  which  the  zones  unite,  see 
the  wood-cut  on  the  next  page,  which  shows  a  portion  of  that  region. 

The  whole  surface  of  the  animal  is  divided  by 
zones,  —  ten  in  number,  five  broader  ones  alter- 
nating with  five  narrow  ones.  The  five  broad 
zones  are  composed  of  large  plates  on  which  are 
the  most  prominent  spines,  attached  to  tubercles 
that  remain  on  the  surface  even  when  the  spines 
drop  off  after  death,  and  mark  the  places  where 
the  spines  have  been.  The  five  small-  zones  are 
perforated  with  regular  rows  of  holes,  and 
through  these  perforations  pass  the  suckers  or 

*  When  reference  is  made  to  the  whole  structure,  including  the 
internal  organs  as  well  as  the  solid  parts  of  the  surface,  the  terms 
actlnal  and  ab-actinal  are  preferable  to  oral  and  ab-oral. 


212  HOMOLOGIES. 

water-tubes  which   are  their  locomotive  appen- 
dages.    For  this  reason  these  narrower  zones  are 


Portion  of  Sea-Urchin  representing  one  narrow  zone  with  a  part  of  the  broad 
zones  on  either  side  and  the  ab-oral  area  on  the  summit. 

called  the  ambulacra,  while  the  broader  zones  in- 
tervening between  them  and  supporting  the 
spines  are  called  the  inter  ambulacra.  Motion, 
however,  is  not  the  only  function  of  these  suck- 
ers ;  they  are  subservient  also  to  respiration  and 
circulation,  taking  in  water,  which  is  conveyed 
through  them  into  various  parts  of  the  body. 

The  oral  aperture  is  occupied  by  five  sets  of 
pieces,  which  may  be  called  jaws,  remembering 
always  that  here  again  this  word  signifies  the 
function,  and  not  the  structure  usually  associated 
with  the  presence  of  jaws  in  the  higher  animals  ; 
and  each  of  these  jaws  terminates  with  a  tooth, 
set  in  its  centre.  Even  the  mode  of  eating  in 
these  animals  is  controlled  by  their  radiate  struc- 
ture ;  for  these  jaws,  evenly  distributed  about  the 


HOMOLOGIES.  213 

circular  oral  aperture,  open  to  receive  the  prey, 
and  then  are  brought  together  to  crush  it,  the 
points  meeting  in  the  centre,  thus  working  con- 
centrically instead  of  moving  up  and  down  or 
from  right  to  left,  as  in  other  animals.  From 
the  oral  opening  the  ten  zones  diverge,  spreading 
over  the  whole  surface,  like  the  ribs  on  a  melon, 
and  converging  in  the  opposite  direction  till  they 
meet  in  a  small  space  which  we  have  called  the 
ab-oral  region  opposite  the  starting-point. 

Here  the  broad  zones  terminate  in  five  large 
plates  differing  somewhat  from  those  that  form 
the  zones  in  other  parts  of  the  body,  and  called 
ovarian  plates,  because  the  eggs  pass  out  through 
certain  openings  in  them ;  while  the  five  narrow 
zones  terminate  in  five  small  plates  on  each  of 
which  is  an  eye,  making  thus  five  eyes  alternating 
with  five  ovarian  plates.  The  centre  of  this  area 
containing  the  ovarian  plates  and  the  visual 
plates  is  filled  up  with  small  movable  plates  clos- 
ing the  space  between  them.  I  should  add,  that 
one  of  the  five  ovarian  plates  is  larger  than  the 
other  four,  and  has  a  peculiar  structure,  long  a 
puzzle  to  naturalists.  It  is  perforated  .with  mi- 
nute holes,  forming  an  exceedingly  delicate  sieve, 
and  this  is  actually  the  purpose  it  serves.  It  is, 
as  it  were,  a  filter,  and  opens  into  a  canal  which 
conducts  water  through  the  interior  of  the  body  ; 
closed  by  this  sieve  on  the  outside,  all  the  water 


214 


HOMOLOGIES. 


that  passes  into  it  is  purified  from  all  foreign 
substances  that  might  be  injurious  to  the  animal, 
and  is  thus  fitted  to  pass  into  the  water-system, 
from  which  arise  the  main  branches  leading  to 
the  minute  suckers  projecting  through  the  holes 
in  the  narrow  zones  of  plates. 

Now,  in  order  to  transform  theoretically  our 
Sea-Urchin  into  a  Star-Fish,  what  have  we  to  do? 
Let  the  reader  imagine  for  a  moment  that  the 
small  ab-oral  area  closing  the  space  between  the 
ovarian  plates  and  the  eye-plates  is  elastic,  and 
may  be  stretched  out  indefinitely ;  then  split  the 
five  broad  zones  along  the  centre,  and  draw  them 
down  to  the  same  level  with  the  mouth,  carry- 
ing the  ovarian  plates  between  them.  We  have 


Star-Fish  from  the  ab-oral  side. 


then  a  star ;  just  as,  dividing,  for  instance,  the 
peel  of  an  orange   into   five  segments,  left,  of 


HOMOLOGIES.  215 

course,  united  at  the  base,  then  stripping  it  off 
and  spreading  it  out  flat,  we  should  have  a  five- 
rayed  star.  But  in  thus  dividing  the  broad  zones 
of  the  Sea-Urchin  into  halves,  we  leave  the 
narrow  zones  in  their  original  relation  to  them, 
except  that  every  narrow  zone,  instead  of  be- 
ing placed  between  two  broad  zones,  has  now 
one  half  of  each  of  the  zones  with  which  it 
alternated  in  the  Sea-Urchin  on  either  side  of 
it,  and  lies  between  them.  The  adjoining  wood- 
cut represents  a  single  ray  of  a  Star-Fish, 


One  arm  of  Star-Fish  from  the  oral  side. 

drawn  from  what  we  call  its  lower  or  oral  side. 
Along  the  centre  of  every  such  ray,  diverging 
from  the  central  opening  or  the  mouth,  we  have 
a  furrow,  corresponding  exactly  to  the  narrower 


216  HOMOLOGIES. 

zones  of  the  Sea-Urchin.  It  is  composed  of  com- 
paratively small  perforated  plates,  through  which 
pass  the  suckers  or  locomotive  appendages ;  and 
on  either  side  of  the  furrows  are  other  plates, 
corresponding  to  the  plates  of  the  broad  zones  in 
the  Sea-Urchin.  Where  shall  we  now  look  for 
the  five  eyes  ?  Of  course,  at  the  tip  of  every  ray ; 
exactly  where  they  were  when  the  rays  were 
drawn  up  to  form  the  summit  of  a  sphere,  for 
then  the  eyes,  which  are  now  at  the  extremities 
of  the  rays,  were  clustered  together  near  the  point 
of  meeting  of  the  five  zones  on  the  ab-oral  side 
of  the  Sea-Urchin.  Where  shall  we  look  for  the 
ovarian  plates  ?  At  each  angle  of  the  five  rays, 
because,  when  the  broad  zones  of  which  they 
formed  the  summit  were  divided,  they  followed 
the  split,  and  now  occupy  the  place  which, 
though  seemingly  so  different  on  the  surface  of 
the  Star-Fish,  is  nevertheless,  relatively  to  the 
rest  of  the  body,  the  same  as  they  occupied  in 
the  Sea-Urchin.  Assuming,  as  we  premised,  that 
the  central  area  of 'the  ab-oral  region,  forming 
the  space  between  the  plates  at  the  summit  of  the 
zones  in  the  Sea-Urchin,  is  elastic,  it  has  stretched 
with  the  spreading  out  of  the  zones,  following  the 
indentation  between  the  rays,  and  now  forms  the 
whole  upper  surface  of  the  body.  All  the  inter- 
nal organs  of  the  animal  lie  between  the  oral  and 
the  ab-oral  regions,  just  as  they  did  in  the  Sea- 


HOMOLOGIES.  217 

Urchin,  only  that  in  the  Star-Fish  these  regions 
are  coequal  in  extent,  while  in  the  Sea-Urchin 
the  ab-oral  region  is  very  contracted,  and  the 
oral  region,  with  the  parts  belonging  to  it,  occu- 
pies the  greater  part  of  its  surface. 

Such  being  the  identity  of  parts  between  a 
Star-Fish  and  a  Sea-Urchin,  let  us  see  now  how 
the  Star-Fish  may  be  transformed  into  the  Pe- 
dunculated  Crinoid,  the  earliest  representative  of 
its  Class,  or  into  a  Comatula,  one  of  the  free  ani- 
mals that  represent  the  Crinoids  in  our  day. 

We  have  seen  that  in  the  Sea-Urchins  the  ab- 
oral  region  is  very  contracted,  the  oral  region 
and  the  parts  radiating  from  it  and  forming  the 
sides  being  the  predominant  features  in  the 
structure ;  and  we  shall  find,  as  we  proceed  in 
our  comparison,  that  the  different  proportions  of 
these  three  parts,  the  oral  and  ab-oral  regions  and 
the  sides,  determine  the  different  outlines  of  the 
various  Orders  in  this  Class.  In  the  Sea-Urchin 
the  oral  region  and  the  sides  are  predominant, 
while  the  ab-oral  region  is  very  small.  In  the 
Star-Fish,  the  oral  and  ab-oral  regions  are 
brought  into  equal  relations,  neither  preponder- 
ating over  the  other,  and  the  sides  are  compressed, 
so  that,  seen  in  profile,  the  outline  of  the  Star- 
Fish  is  that  of  a  slightly  convex  disk,  instead 
of  a  sphere,  as  in  the  Sea-Urchin.  But  when  wo 
come  to  the  Crinoids,  we  find  that  the  great  prc- 
10 


218 


HOMOLOGIES. 


ponderance  of  the  ab-oral  region  determines  all 
that  peculiarity  of  form  which  distinguishes  them 
from  the  other  Echinoderms,  while  the  oral  region 
is  comparatively  insignificant.  The  ab-oral  region 
in  the  Crinoid  rises  to  form  a  sort  of  cup-like 
or  calyx-like  projection.  The  plates  forming  it, 
which  in  the  Star-Fish  or  the  Sea-Urchin  are 
movable,  are  soldered  together  so  as  to  be  per- 


Crinoicl  with  branching  crown  ;  oral  side  turned  upward. 

fectly  immovable  in  the  Crinoid.     Let  this  seem- 
ing calyx  be  now  prolonged  into  a  stem,  and  we 


HOMOLOGIES.  219 

see  at  once  how  striking  is  the  resemblance  to  a 
flower ;  turn  it  downwards,  an  attitude  which  is 
natural  to  these  Crinoids,  and  the  likeness  to  a 
drooping  lily  is  still  more  remarkable.  The  oral 
region,  with  the  radiating  ambulacra,  is  now  lim- 
ited to  the  small  flat  area  opposite  the  juncture 
of  the  stem  with  the  calyx ;  and  whether  it 
stretches  out  to  form  long  arms,  or  is  more  com- 
pact, so  as  to  close  the  calyx  like  a  cup,  it  seems 
in  either  case  to  form  a  flower-like  crown,  bud- 
like  in  Encrinus  and  other  genera,  and  more  like 
an  open  flower  in  Platycrinus  and  the  like.  In 
these  types  of  Echinoderrns  the  interambulacral 
plates  are  absent ;  there  are  no  rows  of  plates  of 
a  different  kind  alternating  with  the  ambulacral 
ones,  as  in  the  Sea-Urchins  and  Star-Fishes,  but 
the  ab-oral  region  closes  immediately  upon  the 
ambulacra. 

It  seems  a  contradiction  to  say,  that,  though 
these  Crinoids  were  the  only  representatives  of 
their  Class  in  the  early  geological  ages,  while  it 
includes  five  Orders  at  the  present  time,  Echino- 
derms  were  as  numerous  and  various  then  as 
now.  But,  paradoxical  as  it  may  se^m,  this  is 
nevertheless  true,  not  only  for  this  Class,  but  for 
many  others  in  the  Animal  Kingdom.  The  same 
numerical  proportions,  the  same  richness  and 
vividness  of  conception,  were  manifested  in  the 
early  creation  as  now ;  and  though  many  of  the 


220  HOMOLOGIES. 

groups  were  wanting  that  are  most  prominent  in 
modern  geological  periods,  those  that  existed 
were  expressed  in  such  endless  variety  that  the 
Animal  Kingdom  seems  to  have  been  as  full  then 
as  it  is  to-day.  The  Class  of  the  Echinoderms  is 
one  of  the  most  remarkable  instances  of  this  pe- 
culiar distribution.  In  the  Silurian  period,  the 
Crinoids  stood  alone ;  there  were  neither  Ophi- 
uraus,  Asterioids,  Echinoids,  nor  Holothurians  ; 
and  yet  in  one  single  locality,  Lockport,  in  the 
State  of  New  York,  over  an  area  of  not  more 
than  a  few  square  miles,  where  the  Silurian  de- 
posits have  been  carefully  examined,  there  have 
been  found  more  different  Species  of  Echino- 
derms than  are  living  now  along  our  whole 
Atlantic  coast  from  Maine  to  Florida,  where  we 
find  representatives  of  all  the  five  orders  of  the 
class. 

There  is  nothing  more  striking  in  these  early 
populations  than  the  richness  of  the  types.  It 
would  seem  as  if,  before  the  world  was  prepared 
for  the  manifold  existences  that  now  find  their 
home  upon  our  earth,  when  organic  life  was 
limited  by  the  absence  of  many  of  the  physical 
conditions  now  prevalent,  the  whole  wealth  of 
the  Creative  Thought  lavished  itself  upon  the 
forms  first  introduced  upon  the  globe.  After 
thirty  years'  study  of  the  fossil  Crinoids,  I  am 
every  day  astonished  by  some  new  evidence  of 


HOMOLOGIES.  221 

the  ingenuity,  the  invention,  the  skill,  if  I  may  so 
speak,  shown  in  varying  this  single  pattern  of  ani- 
mal life.  When  one  has  become,  by  long  study 
of  Nature,  in  some  sense  intimate  with  the  animal 
creation,  it  is  impossible  not  to  recognize  in  it  the 
immediate  action  of  thought,  and  even  to  special- 
ize the  intellectual  faculties  it  reveals.  It  speaks 
of  an  infinite  power  of  combination  and  analysis, 
of  reminiscence  and  prophecy,  of  that  which  has 
been,  in  eternal  harmony  with  that  which  is  to  be ; 
and  while  we  stand  in  reverence  before  the  grand- 
eur of  the  Creative  Conception  as  a  whole,  there 
breaks  from  it  such  lightness  of  fancy,  such  rich- 
ness of  invention,  such  variety  and  vividness  of 
color,  nay,  even  the  ripple  of  mirthfulness,  —  for 
Nature  has  its  humorous  side  also,  —  that  we 
lose  our  grasp  of  its  completeness  in  wonder  at  its 
details,  and  our  sense  of  its  unity  is  clouded  by 
its  marvellous  fertility.  There  may  seem  to  be 
an  irreverence  in  thus  characterizing  the  Crea- 
tive Thought  by  epithets  which  we  derive  from 
the  exercise  of  our  own  mental  faculties ;  but  it 
is  nevertheless  true,  that,  the  nearer  we  come  to 
Nature,  the  more  does  it  seem  to  us  tfoat  all  our 
intellectual  endowments  are  merely  the  echo  of 
the  Almighty  Mind,  and  that  the  eternal  arche- 
types of  all  manifestations  of  thought  in  man 
are  found  in  the  Creation  of  which  lie  is  the 
crowning  work. 


222  HOMOLOGIES. 

In  no  group  of  the  Animal  Kingdom  is  the 
fertility  of  invention  more  striking  than  in 
the  Crinoids.  They  seem  like  the  productions 
of  one  who  handles  his  work  with  an  infinite 
ease  and  delight,  taking  pleasure  in  presenting 
the  same  thought  under  a  thousand  diiferent  as- 
pects. Some  new  cut  of  the  plates,  some  slight 
change  in  their  relative  position,  is  constantly  va- 
rying their  outlines,  from  a  close  cup  to  an  open 
crown,  from  the  long  pear-shaped  oval  of  the 
calyx  in  some  to  its  circular  or  square  or  pentag- 
onal form  in  others.  An  angle  that  is  simple 
in  one  projects  by  a  fold  of  the  surface  and  be- 
comes a  fluted  column  in  another ;  a  plate  that 
was  smooth  but  now  has  here  a  symmetrical  figure 
upon  it  drawn  in  beaded  lines ;  the  stem  which 
is  perfectly  unbroken  in  one,  except  by  the  trans- 
verse divisions  common  to  them  all,  in  the  next 
puts  out  feathery  plumes  at  every  such  transverse 
break.  In  some  the  plates  of  the  stem  are  all 
rigid  and  firmly  soldered  together ;  in  others  they 
are  articulated  upon  each  other  in  such  a  manner 
as  to  give  it  the  greatest  flexibility,  and  allow 
the  seeming  flower  to  wave  and  bend  upon  its 
stalk.  It  would  require  an  endless  number  of 
illustrations  to  give  even  a  faint  idea  of  the  vari- 
ety of  these  fossil  Crinoids.  There  is  no  change 
that  the  fancy  can  suggest  within  the  limits  of 
the  same  structure  that  does  not  find  expression 


HOMOLOGIES.  223 

among  them.  Since  I  have  become  intimate  with 
their  wonderful  complications,  I  have  sometimes 
amused  myself  with  anticipating  some  new  vari- 
ation of  the  theme,  by  the  introduction  of  some 
undescribed  structural  complication,  and  then 
seeking  for  it  among  the  specimens  at  my  com- 
mand, I  have  rarely  failed  to  find  it  in  one  or 
other  of  these  ever-changing  forms. 

The  modern  Crinoid  without  stem,  or  tho 
Comatula,  though  agreeing  with  the  ancient  in 
all  the  essential  elements  of  structure,  differs 
from  it  in  some  specific  features.  It  drops  its 
stem  when  full  grown,  though  the  ab-oral  region 
still  remains  the  predominant  part  of  the  body, 
and  retains  its  cup-like  or  calyx-like  form.  The 
Comatula3  are  not  abundant,  and  though  repre- 
sented by  a  number  of  Species,  yet  the  type  as  it 
exists  at  present  is  meagre,  in  comparison  to  its 
richness  in  former  times.  Indeed,  this  group  of 
Echinoderms,  which,  in  the  earliest  periods,  was 
the  exponent  of  all  its  kind,  has  dwindled  grad- 
ually, in  proportion  as  other  representatives  of 
the  Class  have  come  in  ;  and  there  exists  only 
one  species  now,  the  Pentacrinus  o£  the  West 
Indies,  which  retains  its  stem  in  its  adult  condi- 
tion. It  is  a  singular  fact,  to  which  I  have  before 
alluded,  and  which  would  seem  to  have  especial 
reference  to  the  maintenance  of  the  same  numeric 
proportions  in  all  times,  that,  while  a  Class  is 


224 


HOMOLOGIES. 


represented  by  few  types,  those  types  are  wonder- 
fully rich  and  varied ;  but  in  proportion  as  other 
expressions  of  the  same  structure  are  introduced, 
the  first  dwindle,  and,  if  they  do  not  entirely  dis- 
appear, become  at  least  much  less  prominent  than 
before. 

There  remain  only  two  other  Orders  to  be  con- 
sidered, the  Ophiurans  and  the  Holothurians. 
The  Ophiurans  approach  the  Crinoids  more 
nearly  than  any  other  group  of  Echinoderms, 
and  in  our  classifications  are  placed  next  above 
them.  In  them  the  ab-oral  region,  which  has 


Ophiuran;  showing  one  ray  from  the  oral  side. 

such  a  remarkable  predominance  in  the  Crinoid, 
has  become  depressed  :  it  no  longer  extends  into 
a  stem,  nor  does  it  even  rise  into  the  calyx-liko 


HOMOLOGIES.  225 

or  cup-like  projection  so  characteristic  of  the  Cri- 
noids, —  though,  when  the  animal  is  living,  the 
ab-oral  side  of  the  disk  is  still  quite  convex. 
The  disk  in  the  Ophiurans  is  small  in  comparison 
to  the  length  of  the  arms,  and  perfectly  circular. 
It  does  not  merge  gradually  into  the  arms,  as  in 
the  Star-Fish,  but  the  arms  start  abruptly  from 
its  periphery.  In  these,  as  in  the  Crinoids,  the 
interambulacral  plates  are  absent,  and  the  inter- 
ambulacral  spaces  are  filled  by  an  encroachment 
of  the  ab-oral  region  upon  them.  There  is  an 
infinite  variety  and  beauty  both  of  form  and  color 
in  these  Sea-Stars.  The  arms  frequently  measure 
many  times  the  diameter  of  the  whole  disk,  and 
are  so  different  in  size  and  ornamentation  in  the 
different  Species,  that,  at  first  sight,  one  might 
take  them  for  animals  entirely  distinct  from  each 
other.  In  some  the  arms  are  comparatively  short, 
and  quite  simple ;  in  others  they  are  very  long, 
and  may  be  either  stretched  to  their  full  length, 
or  partly  contracted,  to  form  a  variety  of  graceful 
curves.  In  some  they  are  fringed  all  along  the 
edges ;  in  others  they  are  so  ramified  that  every 
arm  seems  like  a  little  bush,  as  it  were,  and,  in- 
tertwining with  each  other,  they  make  a  thick 
net-work  all  around  the  animal.  In  the  geological 
succession,  these  Ophiurans  follow  the  Crinoids, 
being  introduced  at  about  the  Carboniferous 
period,  and  perhaps  earlier.  They  have  had 
10  o 


226  HOMOLOGIES. 

their  representatives  in  all  succeeding  times,  and 
are  still  very  numerous  in  the  present  epoch. 

To  show  the  correspondence  of  the  Holothu- 
rians  with  the  typical  formula  of  the  whole  class 
of  Echinoderms,  I  will  return  to  the  Sea-Urchins, 
since  they  are  more  nearly  allied  with  that  Order 
than  with  any  of  the  other  groups.  We  have  seen 
that  the  Sea-Urchins  approach  most  nearly  to  the 
sphere,  and  that  in  them  the  oral  region  and  the 
sides  predominate  so  greatly  over  the  ab-oral 
region,  that  the  latter  is  reduced  to  a  small  area 
on  the  summit  of  the  sphere.  In  order  to  trans- 
form the  Sea-Urchin  into  a  Holothurian,  we  have 
only  to  stretch  it  out  from  end  to  end  till  it  be- 
comes a  cylinder,  with  the  oral  region  or  mouth 
at  one  extremity,  and  the  ab-oral  region,  which, 
in  the  Holothurian,  is  reduced  to  its  minimum, 


Holothurian. 


at  the  other.  The  zones  of  the  Sea-Urchin  now 
extend  as  parallel  rows  on  the  Holothurian,  run- 
ning from  one  end  to  the  other  of  the  long  cylin- 
drical body.  On  account  of  their  form,  some 
of  them  have  been  taken  for  Worms,  and  so  clas- 


HOMOLOGIES.  227 

sified  by  naturalists  ;  but  as  soon  as  their  true 
structure  was  understood,  agreeing  in  every  re- 
spect with  that  of  the  other  Echinoderms,  and 
having  no  affinity  whatever  with  the  articulated 
structure  of  the  Worms,  they  found  their  true 
place  in  our  classifications. 

The  natural  attitude  of  these  animals  is  differ- 
ent from  that  of  the  other  Echinoderms.  They 
lie  on  one  side,  and  move  with  the  oral  opening 
forward ;  and  this  has  been  one  cause  of  the 
mistakes  as  to  their  true  affinity.  But  when  we 
would  compare  animals,  we  should  place  them, 
not  in  the  attitude  which  is  natural  to  them  in 
their  native  element,  but  in  what  I  would  call 
their  normal  position,  —  that  is,  such  a  position  as 
brings  the  corresponding  parts  into  the  same  re- 
lation in  all.  For  instance,  the  natural  attitude 
of  the  Crinoid  is  with  the  ab-oral  region  down- 
ward, attached  to  a  stem,  and  the  oral  region  or 
mouth  upward.  The  Ophiuran  turns  its  oral 
region,  along  which  all  the  suckers  or  ambulacra 
are  arranged,  toward  the  surface  along  which  it 
moves.  The  Star-Fish  does  the  same.  The  Sea- 
Urchin  also  has  its  oral  opening  downward.  But 
the  Holothurian  moves  on  one  side,  mouth  fore- 
most, as  represented  in  the  preceding  wood-cut, 
dragging  itself  onward,  like  all  the  rest,  by  means 
of  its  rows  of  suckers.  If,  now,  we  compare 
these  animals  in  the  various  attitudes  natural  to 


228  HOMOLOGIES. 

them,  we  may  fail  to  recognize  the  identity  of 
parts,  or,  at  least,  it  will  not  strike  us  at  once. 
But  if  we  place  them  all  —  Holothurian,  Sea- 
Urchin,  Star-Fish,  Ophiur an,  and  Crinoid  —  with 
the  oral  or  mouth  side  downward,  for  instance, 
we  shall  see  immediately  that  the  small  area  at 
the  opposite  end  of  the  Holothurian  corresponds 
to  the  area  on  the  top  of  the  Sea-Urchin  ;  that  the 
upper  side  of  the  Star-Fish  is  the  same  region 
enlarged ;  tjiat,  in  the  Ophiuran,  that  region 
makes  one  side  of  the  small  circular  disk ;  while 
in  the  Crinoid  it  is  enlarged  and  extended  to 
make  the  calyx-like  projection  and  stem.  In  the 
same  way,  if  we  place  them  in  the  same  attitude, 
we  shall  see  that  the  long,  straight  rows  of  suck- 
ers along  the  length  of  the  Holothurian,  and  the 
arching  zones  of  suckers  on  the  spherical  body  of 
the  Sea-Urchin,  and  the  furrows  with  the  suckers 
protruding  from  them  along  the  arms  of  the  Star- 
Fish  and  Ophiuran,  and  the  radiating  series  of 
pores  from  the  oral  opening  in  the  Crinoid,  are 
one  and  the  same  thing  in  all,  only  altered  some- 
what in  their  relative  proportion  and  extent. 
Around  the  oral  opening  of  the  Holothurian  there 
are  appendages  capable  of  the  most  extraordinary 
changes,  which  seem  at  first  to  be  peculiar  to 
these  animals,  and  to  have  no  affinity  with  any 
corresponding  feature  in  the  same  Class.  But  a 
closer  investigation  has  shown  them  to  be  only 


HOMOLOGIES.  229 

modifications  of  the  locomotive  suckers  of  the 
Star-Fishes  and  Sea-Urchins,  but  ramifying  to 
such  an  extent  as  to  assume  the  form  of  branch- 
ing feelers.  The  little  tufts  projecting  from  the 
oral  side  in  the  Sea-Urchins,  described  as  gills, 
are  another  form  of  the  same  kind  of  appendage. 
The  Holothurians  have  not  the  hard,  brittle 
surface  of  the  other  Echinoderms ;  on  the  con- 
trary, their  envelope  is  tough  and  leathery,  ca- 
pable of  great  contraction  and  dilatation.  No 
idea  can  be  formed  of  the  beauty  of  these 
animals  either  from  dried  specimens  or  from 
those  preserved  in  alcohol.  Of  course,  in  either 
case,  they  lose  their  color,  become  shrunken,  and 
the  movable  appendages  about  the  mouth  shrivel 
up.  One  who  had  seen  Holothurians  only  as 
preserved  in  museums  would  be  amazed  at  the 
spectacle  of  the  living  animal,  especially  if  his  first 
introduction  should  be  to  one  df  the  deep^  rich 
crimson-colored  species,  such  as  are  found  in  quan- 
tities in  the  Bay  of  Fundy.  I  have  seen  such  an 
animal,  when  first  thrown  into  a  tank  of  sea-water, 
remain  for  a  while  closely  contracted,  looking 
like  a  soft  crimson  ball.  Slowly,  almost  imper- 
ceptibly, as  it  becomes  accustomed  to  its  new 
position,  it  begins  to  elongate ;  the  fringes  creep 
softly  out,  spreading  gradually  all  their  ramifica- 
tions, till  one  end  of  the  animal  seems  crowned 
with  feathery,  crimson  sea-weeds  of  the  most 


230  HOMOLOGIES. 

delicate  tracery.  It  is  much  to  be  regretted  that 
these  lower  marine  animals  are  not  better  known. 
The  plumage  of  the  tropical  birds,  the  down  on 
the  most  brilliant  butterfly's  wing,  are  not  more 
beautiful  in  coloring  than  the  hues  of  many 
Radiates,  and  there  is  no  grace  of  motion  sur- 
passing the  movements  of  some  of  them  in  their 
native  element.  The  habit  of  keeping  marine 
animals  in  tanks  is  happily  growing  constantly 
more  popular,  and  before  long  the  beauty  of  these 
inhabitants  of  the  ocean  will  be  as  familiar  to  us 
as  that  of  Birds  and  Insects.  Many  of  the  most 
beautiful  among  them  are,  however,  difficult  to 
obtain,  and  not  easily  kept  alive  in  confinement, 
so  that  they  are  not  often  seen  in  aquariums. 

Having  thus  endeavored  to  sketch  each  differ- 
ent kind  of  Echinoderm,  let  us  try  to  forget  them 
all  in  their  individuality,  and  think  only  of  the 
structural  formula  that  applies  equally  to  each. 
In  all,  the  body  has  three  distinct  regions,  the 
oral,  the  ab-oral,  and  the  sides  ;  but  by  giving  a 
predominance  to  one  or  the  other  of  these  regions, 
a  variety  of  outlines  characteristic  of  the  differ- 
ent groups  is  produced.  In  all,  the  parts  radiate 
from  the  oral  opening,  and  join  in  the  ab-oral 
region.  In  all,  this  radiation  is  accompanied  by 
rows  of  suckers  following  the  line  of  the  diverging 
rays.  It  is  always  the  same  structure,  but,  en- 
dowed with  the  freedom  of  life,  it  is  never  monot- 


HOMOLOGIES.  231 

onous,  notwithstanding  its  absolute  permanence. 
In  short,  drop  off  the  stem  of  the  Crinoid,  and 
depress  its  calyx  to  form  a  flat  disk,  and  we  have 
an  Ophiuran  ;  expand  that  disk,  and  let  it  merge 
gradually  in  the  arms,  and  we  have  a  Star-Fish  ; 
draw  up  the  rays  of  the  Star-Fish,  and  unite 
them  at  the  tips  so  as  to  form  a  spherical  outline, 
and  we  have  a  Sea-Urchin  ;  stretch  out  the  Sea- 
Urchin  to  form  a  cylinder,  and  we  have  a  Holo- 
thurian. 

And  now  let  me  ask,  —  Is  it  my  ingenuity  that 
has  imposed  upon  these  structures  the  conclusions 
I  have  drawn  from  them  ?  —  have  I  so  combined 
them  in  my  thought  that  they  have  become  to 
me  a  plastic  form,  out  of  which  I  draw  a  Crinoid, 
an  Ophiuran,  a  Star-Fish,  a  Sea-Urchin,  or  a 
Holothurian  at  will  ?  or  is  this  structural  idea 
inherent  in  them  all,  so  that  every  observer  who 
has  a  true  insight  into  their  organization  must 
find  it  written  there  ?  Had  our  scientific  results 
anything  to  do  with  our  inventive  faculties,  every 
naturalist's  conclusions  would  be  colored  by  his 
individual  opinions  ;  but  when  we  find  all  zoolo- 
gists converging  more  and  more  towards  each 
other,  arriving,  as  their  knowledge  increases,  at 
exactly  the  same  views,  then  we  must  believe 
that  these  structures  are  the  Creative  Ideas  in 
living  reality.  In  other  words,  so  far  as  there  is 
truth  in  them,  our  systems  are  what  they  are, 


232  HOMOLOGIES. 

not  because  Aristotle,  Linnaeus,  Cuvier,  or  all 
the  men  who  ever  studied  Nature,  have  so  thought 
and  so  expressed  their  thought,  but  because  God 
so  thought  and  so  expressed  his  thought  in  ma- 
terial forms  when  he  laid  the  plan  of  Creation, 
and  when  man  himself  existed  only  in  the  intel- 
lectual conception  of  his  Maker. 


ALTEBNATE  GENERATIONS.         233 


CHAPTER  XIV. 

ALTERNATE   GENERATIONS. 

IF  I  succeeded  in  explaining  my  subject  clearly 
in  the  last  chapter,  my  readers  will  have  seen 
that  the  five  Orders  of  the  Echiiioderms  are  but 
five  expressions  of  the  came  idea  ;  and  I  will  now 
endeavor  to  show  that  the  same  identity  of  struc- 
tural conception  prevails  also  throughout  the  two 
other  Classes  of  Radiates,  and  further,  that  not 
only  are  the  Orders  within  each  Class  built  upon 
the  same  plan,  but  that  the  three  Classes  them- 
selves, Echinoderms,  Acalephs,  and  Polyps,  are 
also  based  upon  one  organic  formula. 

We  will  first  compare  the  three  Orders  of 
Acalephs,  among  which  the  Hydroids  stand  low- 
est, the  Discophorae  next,  and  the  Ctenophorae 
highest.  The  fact  that  these  animals  have  no 
popular  names  shows  how  little  they  are  known. 
It  is  true  that  we  hear  some  of  them  spoken  of  as 
Jelly -Fishes  ;  but  this  name  is  usually  applied  to 
the  larger  Discophore,  when  it  is  thrown  upon 
the  beach  and  lies  a  shapeless  mass  of  gelatinous 
substance  on  the  sand,  or  is  seen  floating  on  the 


234        ALTERNATE  GENERATIONS. 

surface  of  the  water.  The  name  gives  no  idea  of 
the  animal  as  it  exists  in  full  life  and  activity. 
When  we  speak  of  a  Bird  or  an  Insect,  the  mere 
name  calls  up  at  once  a  characteristic  image  of 
the  thing ;  but  the  name  of  Jelly-Fish,  or  Sun- 
Fish,  or  Sea-Blubber,  as  the  larger  Acalephs  are 
also  called,  suggests  to  most  persons  a  vague  idea 
of  a  fish  with  a  gelatinous  body,  —  or,  if  they 
have  lived  near  the  sea-shore,  they  associate  it 
only  with  the  unsightly  masses  of  jelly-like  sub- 
stance sometimes  strewn  in  thousands  along  the 
beach  after  a  storm.  To  very  few  does  the  term 
recall  either  the  large  Discophore,  with  its  pur- 
ple disk  and  its  long  streamers  floating  perhaps 
twenty  or  thirty  feet  behind  it  as  it  swims,  —  or 
the  Ctenophore,  with  its  more  delicate,  trans- 
parent structure,  and  almost  invisible  fringes  in 
parallel  rows  upon  the  body,  which  decompose 
the  rays  of  light  as  the  creature  moves  through 
the  water,  so  that  hues  of  ruby-red  and  emerald- 
green,  blue,  purple,  yellow,  all  the  colors  of  the 
rainbow,  ripple  constantly  over  its  surface  when 
it  is  in  motion,  —  or  the  Hydroid,  with  its  little 
shrub-like  communities  living  in  tide-pools,  estab- 
lishing themselves  on  rocks,  shells,  or  sea-weeds, 
and  giving  birth  not  only  to  animals  attached 
to  submarine  bodies,  like  themselves,  but  also  to 
free  Medusas  or  Jelly-Fishes  that  in  their  turn 
give  birth  again  to  eggs  which  return  to  the 


ALTERNATE  GENERATIONS.        235 

parent  form,  and  thus,  by  alternate  generations, 
maintain  two  distinct  patterns  of  animal  life 
within  one  cycle  of  growth. 

Perhaps,  of  all  the  three  Classes  of  Radiates, 
Acalephs  are  the  least  known.  The  general 
interest  in  Corals,  has  called  attention  to  the 
Polyps,  and  the  accessible  haunts  of  the  Sea- 
Urchins  and  Star-Fishes  have  made  the  Echino- 
dorms  almost  as  familiar  to  the  ordinary  observer 
as  the  common  sea-shells,  while  the  Acalephs  are 
usually  to  be  found  at  a  greater  distance  from 
the  shore,  and  are  not  easily  kept  in  confinement. 
It  is  true  that  the  Hydroids  live  along  the  shore, 
and  may  be  reared  in  tanks  without  difficulty ; 
but  they  are  small,  and  would  be  often  taken 
for  sea-weeds  by  those  ignorant  of  their  true 
structure.  Thus  this  group  of  animals,  with 
all  their  beauty  of  form,  color,  and  movement, 
and  peculiarly  interesting  from  their  singular 
modes  of  growth,  remains  comparatively  un- 
known except  to  the  professional  naturalist. 

It  may,  therefore,  be  not  uninteresting  or  use 
less  to  my  readers,  if  I  give  some  account  of  the 
appearance  and  habits  of  these  animals,  keeping 
in  view,  at  the  same  time,  my  ultimate  object, 
namely,  to  show  that  they  are  all  founded  on 
the  same  structural  elements  and  have  the  same 
ideal  significance.  I  will  begin  with  some  ac- 
count of  the  Hydroids,  including  the  story  of  the 


236        ALTERNATE  GENERATIONS. 

alternate  generations,  by  which  they  give  birth  to 
Medusae,  while  the  Medusae,  in  their  turn,  repro- 
duce the  Hydroids,  from  which  they  spring.  But 
first,  a  few  words  upon  the  growth  of  Radiates  in 
general. 

There  is  no  more  interesting  series  of  trans- 
formations than  that  of  the  development  of  Ra- 
diates. They  are  all  born  as  little  transparent 
globular  bodies,  covered  with  vibratile  cilia, 
swimming  about  in  this  condition  for  a  longer  or 
shorter  time  ;  then,  tapering  somewhat  at  one 
end  and  broadening  at  the  other,  they  may  be- 
come attached  by  the  narrower  extremity,  while 
at  the  opposite  one  a  depression  takes  place, 
deepening  in  the  centre  till  it  becomes  an  aper- 
ture, and  extending  its  margin  to  form  the  ten- 
tacles. All  Radiates  pass  through  this  Polyp-like 
condition  at  some  period  of  their  lives,  either 
before  or  after  they  are  hatched  from  the  eggs, 
though  they  do  not  all  attach  themselves  per- 
manently. In  some  it  forms  a  marked  period  of 
their  existence,  while  in  others  it  passes  very 
rapidly,  and  is  undergone  within  the  egg ;  but, 
at  whatever  time  and  under  whatever  conditions 
it  occurs,  it  forms  a  necessary  part  of  their  devel- 
opment, and  shows  that  all  these  animals  have 
one  and  the  same  pattern  of  growth. 

This  difference  in  the  relative  importance  and 
duration  of  certain  phases  of  growth  is  by  no 


ALTERNATE  GENERATIONS.         237 

means  peculiar  to  the  Radiates,  but  occurs  in  all 
divisions  of  the  Animal  Kingdom.  There  are 
many  Insects  that  pass  through  their  metamor- 
phoses within  the  egg,  appearing  as  complete 
Insects  at  the  moment  of  their  birth  ;  but  the 
series  of  changes  is  nevertheless  analogous  to 
that  of  the  Butterfly,  whose  existence  as  Worm, 
Chrysalis,  and  Winged  Insect  is  so  well  known 
to  all.  Take  the  Grasshopper,  for  instance : 
with  the  exception  of  the  wings,  it  is  born  in 
its  mature  form  ;  but  within  the  egg  it  has  had 
its  Worm-like  stage  as  much  as  the  Butterfly 
that  we  knew  a  few  months  ago  as  a  Caterpillar. 
In  the  same  way  certain  of  the  higher  Radiates 
undergo  all  their  transformations,  from  the  Polyp 
phase  of  growth  to  that  of  Acaleph  or  Echino- 
derm,  after  birth ;  while  others  pass  rapidly 
through  the  lower  phases  of  their  existence 
within  the  egg,  and  are  born  in  their  final  con- 
dition, when  all  their  intermediate  changes  have 
been  completed. 

We  have  appropriate  names  for  all  the  aspects 
of  life  in  the  Insect :  we  call  it  Larva  in  its  first 
or  Worm-like  period,  Chrysalis  in  its  second  or 
Crustacean-like  phase  of  life,  and  Imago  in  its 
third  and  last  condition  as  Winged  Insect.  But 
the  metamorphoses  of  the  Radiates  are  too  little 
known  to  be  characterized  by  popular  names  ; 
and  when  they  were  first  traced,  the  relation 


238        ALTERNATE  GENERATIONS. 

between  their  different  phases  of  existence  was 
not  understood,  so  that  the  same  animal  in  differ- 
ent stages  of  growth  has  frequently  been  described 
as  two  or  more  distinct  animals.  This  has  led  to 
a  confusion  in  our  nomenclature  much  to  be 
regretted  ;  for,  however  inappropriate  it  may  be, 
a  name  once  accepted  and  passed  into  general 
use  is  not  easily  changed. 

That  early  stage  of  growth,  common  to  all 
Radiates,  in  which  they  resemble  the  Polyps,  has 
been  called  the  Hydra  state,  in  consequence  of 
their  resemblance  to  the  fresh-water  Hydra  to  be 
found  in  quantities  on  the  under  side  of  Duck- 
Weed  and  Lily-pads.  For  any  one  that  cares  to 
examine  these  animals,  it  may  be  well  to  mention 
that  they  are  easily  found  and  thrive  well  in 
confinement.  Dip  a  pitcher  into  any  pool  of 
fresh  water  where  Duck-Weed  or  Lilies  are 
growing  in  the  summer,  and  you  are  sure  to 
bring  up  hundreds  of  these  fresh- water  Hydra3, 
swarming  in  myriads  in  all  our  ponds.  In  a  glass 
bowl  their  motions  are  easily  watched  ;  and  a 
great  deal  may  be  learned  of  their  habits  and  mode 
of  life,  with  little  trouble.  Such  an  animal 
soon  completes  its  growth  :  for  the  stage  which  I 
have  spoken  of  as  transient  for  the  higher  Radi- 
ates is  permanent  for  these ;  and  when  the  little 
sphere  moving  about  by  means  of  its  vibratile 
cilia  has  elongated  a  little,  attached  itself  by  the 


ALTERNATE  GENERATIONS. 


239 


lower  end  to  some  surface,  while  the  inversion  of 
the  upper  end  has  formed  the  mouth  and  diges- 
tive cavity,  and  the  expansion  of  its  margin  has 
made  the  tentacles,  the  very  simple  story  of  the 
fresh-water  Hydra  is  told.  But  the  last  page  in 
the  development  of  these  lower  Radiates  is  but 
the  opening  chapter  in  that  of  the  higher  ones, 
and  I  will  give  some  account  of  their  trans- 
formations as  they  have  been  observed  in  the 
Acalephs. 

On  shells  and  stones,  on  sea-weeds  or  on 
floating  logs,  there  may  often  be  observed  a 
growth  of  exquisitely  delicate  branches,  look- 
ing at  first  sight  more  like  a  small  bunch  of 
moss  than  anything  else.  But  gather  such  a 


Coryne  mirabilis,  natural  size. 

mossy  tuft  and  place  it  in  a  glass  bowl  filled 
with  sea-water,  and  you  will  presently  find  that 
it  is  full  of  life  and  activity.  Every  branch  of 
this  miniature  shrub  terminates  in  a  little  club- 
shaped  head,  upon  which  are  scattered  a  num- 
ber of  tentacles.  They  are  in  constant  motion, 


240        ALTERNATE  GENERATIONS. 

extending  and  contracting  their  tentacles,  some 
of  the    heads    stretched   upwards,    others    bent 


Single  head  or  branch  of  Coryne  mirabilis,  magnified,  with  two  Medusa  buds. 

downwards,  all  seeming  very  busy  and  active. 
Each  tentacle  has  a  globular  tip  filled  with  a 
multitude  of  cells,  the  so-called  lasso-cells,  each 
one  of  which  conceals  a  coiled-up  thread.  These 
organs  serve  to  seize  the  prey,  shooting  out 
their  long  threads,  thus  entangling  the  victim 
in  a  net  more  delicate  than  the  finest  spider's 
web,  and  then  carrying  it  to  the  mouth  by 
the  aid  of  the  lower  part  of  the  tentacle.  The 
complication  of  structure  in  these  animals,  a 
whole  community  of  which,  numbering  from 
twenty  to  thirty  individuals,  is  not  more  than 
an  inch  in  height,  is  truly  wonderful.  In  such 


ALTEENATE  GENERATIONS.        241 

a  community  the  different  animals  are  hardly 
larger  than  a  good-sized  pin's  head ;  and  yet 
every  individual  has  a  digestive  cavity  and  a 
complete  system  of  circulation. 

Its  body  consists  of  a  cavity  enclosed  in  a 
double  wall,  continuing  along  the  whole  length 
of  each  branch  till  it  joins  the  common  stem 
forming  the  base  of  the  stock.  In  this  cavity 
the  food  becomes  softened  and  liquefied  by  the 
water  that  enters  with  it  through  the  mouth,  and 
is  thus  transformed  into  a  circulating  fluid  which 
flows  from  each  head  to  the  very  base  of  the 
community  and  back  again.  The  inner  surface 
of  the  digestive  cavity  is  lined  with  brownish-red 
granules,  which  probably  aid  in  the  process  of 
digestion ;  they  frequently  become  loosened,  fall 
into  the  circulating  fluid,  and  may  be  seen  borne 
along  the  stream  as  it  passes  up  and  down.  The 
rosy  tint  of  the  little  community  is  due  to  these 
reddish  granules. 

This  crowd  of  beings  united  in  a  common  life 
began  as  one  such  little  Hydra-like  animal  as  I 
have  described  above,  —  floating  free  at  first, 
then  becoming  attached,  and  growing  into  a 
populous  stock  by  putting  out  buds  at  different 
heights  along  the  length  of  the  stem.  The  for- 
mation of  such  a  bud  is  very  simple,  produced 
by  the  folding  outwardly  of  the  double  wall  of 
the  body,  appearing  first  as  a  slight  projection 
11  p 


242        ALTEKNATE  GENERATIONS. 

of  the  stem  sideways,  which  elongates  gradually, 
putting  out  tentacles  as  it  grows  longer,  while 
at  the  upper  end  an  aperture  is  formed  to  make 
the  mouth.  This  is  one  of  the  lower  group 
of  Radiates,  known  as  Hydroids,  and  long  be- 
lieved to  be  Polyps,  from  their  mode  of  living 
in  communities  and  reproducing  their  kind  by 
budding,  after  the  fashion  of  Corals. 

But  if  such  a  little  tuft  of  Hydroids  has  been 
gathered  in  spring,  a  close  observer  may  have 
an  opportunity  of  watching  the  growth  of  an- 
other kind  of  individual  from  it,  which  would 
seem  to  show  its  alliance  with  the  Acalephs 
rather  than  the  Polyps.  At  any  time  late  in 
February  or  early  in  March,  bulb-like  projec- 
tions, more  globular  than  the  somewhat  elon- 
gated buds  of  the  true  Hydroid  heads,  may  be 
seen  growing  either  among  the  tentacles  of  one 
of  these  little  animals,  or  just  below  the  head 
where  it  merges  in  the  stem.*  Very  delicate 
and  transparent  in  substance,  it  is  hardly  per- 
ceptible at  first;  and  the  gradual  formation  of 
its  internal  structure  is  the  less  easily  discerned, 
because  a  horny  sheath,  forming  the  outer  cover- 
ing of  the  Hydroid  stock,  extends  to  enclose  and 
shield  the  new-comer,  whom  we  shall  see  to  be 
so  different  from  the  animal  that  gives  it  birth 
that  one  would  suppose  the  Hydroid  parent  must 

*  See  wood-cut,  p.  240. 


ALTERNATE  GENERATIONS.        243 

be  as  much  surprised  at  the  sight  of  its  off- 
spring as  the  Hen  that  has  accidentally  hatched 
a  Duck's  egg.  At  the  right  moment  this  film 
is  torn  open  by  the  convulsive  contractions  of 
the  animal,  which,  thus  freed  from  its  envelope, 
begins  at  once  to  expand.  By  this  time  the 
little  bud  has  assumed  the  form  of  a  Medusoid 
or  Jelly-Fish  disk,  with  its  four  tubes  radiating 
from  the  central  cavity.  The  proboscis,  so  char- 
acteristic of  all  Jelly-Fishes,  hangs  from  the  cen- 
tral opening ;  and  the  tentacles,  coiled  within 
the  internal  cavity  up  to  this  time,  now  make 
their  appearance,  and  we  have  a  complete  little 
Medusa  growing  upon  the  Hydroid  head.  Gradu- 
ally the  point  by  which  it  is  attached  to  the 
parent-stock  narrows  and  becomes  more  and 
more  contracted,  till  the  animal  drops  off  and 
swims  away,  a  free  Jelly-Fish. 

The  substance  of  these  animals  seems  to  have 
hardly  more  density  or  solidity  than  their  native 
element.  I  remember  showing  one  to  a  friend 
who  had  never  seen  such  an  animal  before,  and, 
after  watching  its  graceful  motions  for  a  moment 
in  the  glass  bowl  where  it  was  swimming,  he 
asked,  "Is  it  anything  more  than  organized 
water  ?  "  The  question  was  very  descriptive ;  for 
so  little  did  it  seem  to  differ  in  substance  from 
the  water  in  which  it  floated  that  one  might 
well  fancy  that  some  drops  had  taken  upon 


244        ALTERNATE  GENERATIONS. 

themselves  organic  structure,  and  had  begun  to 
live  and  move.  It  swims  by  means  of  rapid 
contractions  and  expansions  of  its  disk,  thus 
impelling  itself  through  the  water,  its  tentacles 
floating  behind  it  and  measuring  many  times 
the  length  of  the  body.  The  disk  is  very  con- 


Little  J«lly-Fish,  called  Sarsia,  the  free  Medusa  of  Coryne  mirabilis. 

vex,  as  will  be  seen  by  the  wood-cut ;  four  tubes 
radiate  from  the  central  cavity  to  the  periphery, 


ALTERNATE  GENERATIONS.        245 

where  they  unite  in  a  circular  tube  around  the 
margin  and  connect  also  with  the  four  tenta- 
cles ;  from  the  centre  of  the  lower  surface  hangs 
the  proboscis,  terminating  in  a  mouth.  Not- 
withstanding the  delicate  structure  of  this  little 
being,  it  is  exceedingly  voracious.  It  places  it- 
self upon  the  surface  of  the  animal  on  which 
it  feeds,  and,  if  it  have  any  hard  parts,  it  simply 
sucks  the  juices,  dropping  the  dead  carcass  im- 
mediately after ;  but  it  swallows  whole  the  little 
Acalephs  of  other  Species  and  other  soft  ani- 
mals that  come  in  its  way.--  Early  in  summer 
these  Jelly-Fishes  drop  their  eggs,  little  trans- 
parent pear-shaped  bodies,  covered  with  vibratile 
cilia.  They  swim  about  for  a  time,  until  they 
have  found  a  resting-place,  where  they  attach 
themselves,  each  one  founding  a  Hydroid  stock 
of  its  own,  which  will  in  time  produce  a  new 
brood  of  Medusae. 

This  series  of  facts,  presented  here  in  their 
connection,  had  been  observed  separately  before 
their  true  relation  was  understood.  Investigations 
had  been  made  on  the  Hydroid  stock,  described 
as  Coryne,  and  upon  its  Medusoid  offspring,  de- 
scribed as  Sarsia,  named  after  the  naturalist  Sars, 
whose  beautiful  papers  upon  this  class  of  animals 
have  associated  his  name  with  it ;  but  the  inves- 
tigations by  which  all  these  facts  have  been  asso- 
ciated in  one  connected  series  are  very  recent. 


246        ALTERNATE  GENERATIONS. 

These  transformations  do  not  correspond  to  our 
common  idea  of  metamorphoses,  as  observed  in 
the  Insect,  for  instance.  In  the  Butterfly's  life 
we  have  always  one  and  the  same  individual,  — 
the  Caterpillar  passing  into  the  Chrysalis  state, 
and  the  Chrysalis  passing  into  the  condition  of 
the  Winged  Insect.  But  in  the  case  I  have  been 
describing,  while  the  Hydroid  gives  birth  to  the 
Medusa,  it  still  preserves  its  own  distinct  exist- 
ence ;  and  the  different  forms  developed  on  one 
stock  seem  to  be  two  parallel  lives,  and  not  the 
various  phases  of  one  and  the  same  life.  This 
group  of  Hydroids  retains  the  name  of  Coryne  ;  * 
and  the  Medusa  born  from  it,  the  Sarsia  (repre- 
sented on  p.  244),  has  received,  as  I  have  said, 
the  name  of  the  distinguished  investigator  to 
whose  labors  we  owe  much  of  our  present  knowl- 
edge of  these  animals.  Let  us  look  now  at  an- 
other group  of  Hydroids,  whose  mode  of  develop- 
ment is  equally  curious  and  interesting. 

The  little  transparent  embryos  from  which  they 
arise,  oval  in  form,  with  a  slight,  scarcely  percep- 
tible depression  at  one  end,  resemble  the  embryos 
of  Coryne  already  described.  They  may  be  seen 
in  great  numbers  in  the  autumn,  floating  about  in 
the  water,  or  rather  swimming,  —  for  the  motion 
of  all  Kadiates  in  their  earliest  stage  of  existence 
is  rapid  and  constant,  in  consequence  of  the  vi- 

*  See  wood-cut,  p.  239 


ALTERNATE  GENERATIONS.        247 

bratile  cilia  that  cover  the  surface.  At  this  stage 
of  its  existence  such  an  embryo  is  perfectly  free, 
but  presently  its  wandering  life  comes  to  an  end : 
it  shows  a  disposition  to  become  fixed,  and  pro- 
ceeds to  choose  a  suitable  resting-place.  I  use 
the  word  "  choose  "  advisedly ;  for  though  at  this 
time  the  little  embryo  seems  to  have  no  developed 
organs,  it  yet  exercises  a  certain  discrimination 
in  its  selection  of  a  home.  Slightly  pear-shaped 
in  form,  it  settles  down  upon  its  narrower  end. 
It  wavqrs  and  sways  to  and  fro,  as  if  trying  to  get 
a  firm  foot-hold,  and  force  itself  down  upon  the 
surface  to  which  it  adheres;  but  presently,  as  if 
dissatisfied  with  the  spot  it  has  chosen,  it  sud- 
denly breaks  loose  and  swims  away  to  another 
locality,  where  the  same  examination  is  repeated, 
not  more  to  its  own  satisfaction  apparently,  for 
the  creature  will  renew  the  experiment  half  a 
dozen  times,  perhaps,  before  making  a  final  selec- 
tion, and  becoming  permanently  attached  to  the 
soil.  In  the  course  of  this  process  the  lower  end 
becomes  flattened,  and  moulds  itself  to  the  shape 
of  the  body  on  which  it  rests.  Once  settled,  this 
animal,  thus  far  hardly  more  than  a  transparent 
oblong  body,  without  any  distinct  organs,  begins 
to  develop  rapidly.  It  elongates,  forming  a  kind 
of  cup-like  base  or  stem ;  the  upper  end  spreads 
somewhat ;  the  depression  at  its  centre  deepens  ; 
a  mouth  is  formed  that  gapes  widely,  and  opens 


248        ALTEENATE  GENERATIONS. 

into  the  digestive  cavity ;  and  the  upper  margin 
spreads  out  to  form  a  number  of  tentacles,  few  at 
first,  but  growing  more  and  more  numerous,  till 
a  wreath  is  completed  all  around  it.  In  this  con- 
dition the  young  Jelly-Fish  has  been  described 
under  the  name  of  Scyphostoma.  As  soon  as  the 


Scyphostoma  of  Aurelia  flavidula,  the  white  Jelly-Fish  with  a  rosy  cross,  com- 
mon along  the  coasts  of  New  England. 

wreath  of  tentacles  is  complete,  a  constriction 
takes  place  below  it,  thus  separating  the  upper 
portion  of  the  animal  from  the  lower  by  a  marked 
dividing-line.  Presently  a  second  constriction 
takes  place  below  the  first,  then  a  third,  till  the 
entire  length  of  the  animal  is  divided  across  by  a 
number  of  such  transverse  constrictions,  the  whole 
body  growing,  meanwhile,  in  height.  But  now  an 
extraordinary  change  takes  place  in  the  portions 
thus  divided  off.  Each  one  assumes  a  distinct 
organic  structure,  as  if  it  had  an  individual  life 
of  its  own.  The  margin  becomes  lobed  in  eight 
deep  scallops,  and  a  tube  or  canal  runs  through 
the  centre  of  each  such  lobe  to  the  centre  of  the 


ALTERNATE  GENERATIONS.        249 

body,  where  a  digestive  cavity  is  already  formed. 
At  this  time  the  constrictions  have  deepened,  so 
that  the  margins  of  all  the  successive  divisions  of 
the  little  Hydroid  are  very  prominent,  and  the 
whole  animal  looks  like  a  pile  of  saucers,  or  of 
disks  with  scalloped  edges,  and  the  convex  side 
turned  downward.  Its  general  aspect  may  be 
compared  to  a  string  of  Lilac-blossoms,  such  as 
the  children  make  for  necklaces  in  the  spring,  in 


Strobila  of  Aurelia  flavidula. 

which  the  base  of  one  blossom  is  inserted  into  the 
tipper  side  of  the  one  below  it.  In  this  condition 
our  Jelly-Fish  has  been  called  Strobila. 

While  these  organic  changes  take  place  in  the 
lower  disks,  the  topmost  one,  forming  the  summit 
of  the  pile  and  bearing  the  tentacles,  undergoes 
no  such  modification  ;  but  presently  the  first  con- 
striction dividing  it  from  the  rest  deepens  to  such 
11* 


250        ALTERNATE  GENERATIONS. 

a  degree  that  it  remains  united  to  them  by  a 
mere  thread  only,  and  it  soon  breaks  off  and  dies. 
This  is  the  signal  for  the  breaking  up  of  the  whole 
pile  in  the  same  way  by  the  deepening  of  the  con- 
strictions ;  but,  instead  of  dying,  as  they  part, 
they  begin  a  new  existence  as  free  Medusas.  Only 
the  lowest  portion  of  the  body  remains,  and  around 
its  margin  new  tentacles  are  developed,  corre- 
sponding to  those  which  crowned  the  first  little 
embryo.  This  repeats  the  whole  history  again, 


Strobila  of  Aurelia  flavidula :    a,  Scyphostoma  reproduced  at  the  base  of  a 
Strobila,  all  the  disks  of  which  have  dropped  off  but  the  last,  b  b. 

as  it  grows  up  during  the  following  season  to 
divide  itself  anew  into  disks,  like  its  predecessor. 
As  each  individual, separates  from  the  commu- 
nity of  which  it  has  made  a  part,  it  reverses  its 
position,  and,  instead  of  turning  the  margin  of 
the  disk  upward,  it  turns  it  downward,  thus 
bringing  the  mouth  below,  and  the  curve  of  the 
disk  above.  These  free  individuals  have  been 
described  under  the  name  of  Ephyra.  This  is 
the  third  phase  of  the  existence  of  our  Jelly-Fish. 
It  swims  freely  about,  a  transparent,  umbrella- 


ALTERNATE  GENERATIONS.        251 

like  disk,  with  a  proboscis  hanging  from  the  lower 
side,  which,  to  complete  the  comparison,  we  may 
call  the  handle  of  the  umbrella.  The  margin  of 
the  disk  is  even  more  deeply  lobed  than  in  the 
Hydroid  condition,  and  in  the  middle  of  each  lobe 
is  a  second  depression,  quite  deep  and  narrow,  at 


Ephyra  or  Aurelia  flavidula. 

the  base  of  which  is  an  eye.  How  far  such  organs 
are  gifted  with  the  power  of  vision  we  cannot  de- 
cide ;  but  the  cells  of  which  they  are  composed 
certainly  serve  the  purpose  of  facets,  of  lenses 
and  prisms,  and  must  convey  to  the  animal  a 
more  or  less  distinct  perception  of  light  and  color. 
The  lobes  are  eight  in  number,  as  before,  with  a 
tube  diverging  from  the  centre  of  the  body  into 
each  lobe.  Shorter  tubes  between  the  lobes  alter- 
nate with  these,  making  thus  sixteen  radiating 
tubes,  all  ramifying  more  or  less. 

From  this  stage  to  its  adult  condition,  the 
animal  undergoes  a  succession  of  changes  in 
the  gradual  course  of  its  growth,  uninterrupted, 
however,  by  any  such  abrupt  transition  as  that 


252 


ALTERNATE   GENERATIONS. 


by  which  it  began  its  life  as  a  free  animal.     The 
lobes  are  gradually  obliterated,  so  that  the  mar- 


• 

o 

Aurelia  flavidula,  the  common  white  Jelly-Fish  of  our  sea-shores,  seen  from 
above  :  c,  mouth  ;  e  e  e  eee,  eyes  ;  mm  mm,  lobes  or  curtain  of  the  mouth 
in  outlines  -,  o  o  o,  ovaries  ;  1 1 1 ,  tentacles  ;  w  w,  ramified  tubes. 


gin  becomes  almost  an  unbroken  circle.  The 
eight  eyes  were,  as  I  have  said,  at  the  bottom  of 
depressions  in  the  centre  of  the  several  lobes  ; 
but,  by  the  equalizing  of  the  marginal  line,  the 
gradual  levelling,  as  it  were,  of  all  the  inequali- 
ties of  the  edge,  the  eyes  are  pushed  out,  and 
occupy  eight  spots  on  the  margin,  where  a  faint 
indentation  only  marks  what  was  before  a  deep 
cut  in  the  lobe.  The  eight  tubes  of  the  lobes 
have  extended  in  like  manner  to  the  edge,  and 


ALTERNATE  GENERATIONS.        253 

join  it  just  at  the  point  where  the  eyes  are 
placed,  so  that  the  extremity  of  each  tube 
unites  with  the  base  of  each  eye.  Those  parts 
of  the  margin  filling  the  spaces  between  the 
eyes  correspond  to  the  depressions  dividing  the 
lobes  or  scallops  in  the  earlier  stage,  and  to 
these  radiate  the  eight  other  tubes  alternating 
with  the  eye-tubes,  now  divided  into  numerous 
branches.  Along  each  of  these  spaces  is  devel- 
oped a  fine,  delicate  fringe  of  tentacles,  hanging 
down  like  a  veil  when  the  animal  is  at  rest,  or 
swept  back  when  it  is  in  motion.  In  the  previous 
stage,  the  tubes  ramified  toward  the  margin ;  but 
now  they  branch  at  or  near  their  point  of  starting 
from  the  central  cavity,  so  extensively  that  every 
part  of  the  body  is  traversed  by  these  collateral 
tubes,  and  when  one  looks  down  at  it  from  above 
through  the  gelatinous  transparent  disk,  the  nu- 
merous ramifications  resemble  the  fine  fibrous 
structure  of  a  leaf  with  its  net-work  of  nervules. 

On  the  lower  side,  or  what  I  have  called  in  a 
previous  chapter  the  oral  region  of  the  animal,  a 
wonderfully  complicated  aparatus  is  developed. 
The  mouth  projects  in  four  angles,  arid  at  each 
such  angle  a  curtain  arises,  stretching  outwardly, 
and  sometimes  extending  as  far  as  the  margin. 
These  curtains  are  fringed  and  folded  on  the 
lower  edge,  so  that  they  look  like  four  ruffled 
flounces  hanging  from  the  lower  side  of  the 


254        ALTERNATE  GENERATIONS. 

animal.  On  the  upper  side  of  the  body,  but 
alternating  in  position  with  these  curtains,  are 
the  four  ovaries,  crescent-like  in  shape,  and  so 
placed  as  to  form  the  figure  of  a  cross,  when  seen 
from  above  through  the  transparency  of  the  disk. 
I  should  add,  that,  though  I  speak  of  some  organs 
as  being  on  the  upper  and  others  on  the  lower 
side  of  the  body,  all  are  under  the  convex, 
arched  surface  of  the  disk,  which  is  gelatinous 
throughout,  and  simply  forms  a  transparent 
vaulted  roof,  as  it  were,  above  the  rest  of  the 
body. 


Aurelia  flavidula,  seen  in  profile. 

When  these  animals  first  make  their  appear- 
ance in  the  spring,  they  may  be  seen,  when  the 
sky  is  clear  and  the  sea  smooth,  floating  in  im- 
mense numbers  near  the  surface  of  the  water, 
though  they  do  not  seek  the  glare  of  the  sun, 
but  are  more  often  found  about  sheltered  places, 
in  the  neighborhood  of  wharves  or  overhanging 
rocks.  As  they  grow  larger,  they  lose  something 
of  their  gregarious  disposition,  —  they  scatter 


ALTEKNATE  GENERATIONS.        255 

more  ;  and  at  this  time  they  prefer  the  sunniest 
exposures,  and  like  to  bask  in  the  light  and 
warmth.  They  assume  every  variety  of  attitude, 
but  move  always  by  the  regular  contraction  and 
expansion  of  the  disk,  which  rises  and  falls  with 
rhythmical  alternations,  the  average  number  of 
these  movements  being  from  twelve  to  fifteen  in 
a  minute.  There  can  be  no  doubt  that  they 
perceive  what  is  going  on  about  them,  and  are 
very  sensitive  to  changes  in  the  state  of  the 
atmosphere ;  for,  as  soon  as  the  surface  of  the 
water  is  ruffled,  or  the  sky  becomes  overcast, 
they  sink  into  deeper  water,  and  vanish  out  of 
sight.  When  approached  with  a  dip-net,  it  is 
evident,  from  the  acceleration  of  their  move- 
ments, that  they  are  attempting  to  escape. 

At  the  spawning  season,  toward  the  end  of 
July  or  the  beginning  of  August,  they  gather 
again  in  close  clusters.  At  this  period  I  have 
seen  them  at  Nahant  in  large  shoals,  covering  a 
space  of  fifty  feet  or  more,  and  packed  so  closely 
in  one  unbroken  mass  that  an  oar  could  not  be 
thrust  between  them  without  injuring  many.  So 
deep  was  the  phalanx  that  I  could  not  "ascertain 
how  far  it  extended  below  the  surface  of  the 
water,  and  those  in  the  uppermost  layer  were 
partially  forced  out  of  the  water  by  the  pressure 
of  those  below. 

It  is  not  strange  that  the  relation  between  the 


256        ALTERNATE  GENERATIONS. 

various  phases  of  this  extraordinary  series  of 
metamorphoses,  so  different  from  each  other  in 
their  external  aspects,  should  not  have  been 
recognized  at  once,  and  that  this  singular  Aca- 
leph  should  have  been  called  Scyphostoma  in  its 
simple  Hydroid  condition  (see  p.  248),  Strobila 
after  the  transverse  division  of  the  body  had  taken 
place  (see  p.  249),  Ephyra  in  the  first  stages  of 
its  free  existence  (see  p.  251),  and  Aurelia  in  its 
adult  state  (see  pp.  252  and  254),  —  being  thus 
described  as  four  distinct  animals.  These  vari- 
ous forms  are  now  rightly  considered  as  the  suc- 
cessive stages  of  a  development  intimately  con- 
nected in  all  its  parts,  —  beginning  with  the 
simple  Hydroid  attached  to  the  ground,  and  clos- 
ing in  the  shape  of  our  common  Aurelia,  with 
its  white  transparent  disk,  its  silky  fringe  of 
tentacles  around  the  margin,  its  ruffled  curtains 
hanging  from  the  mouth,  and  its  four  crescent- 
shaped  ovaries  grouped  to  form  a  cross  on  the 
summit.  From  these  ovaries  a  new  brood  of 
little  embryos  is  shed  in  due  time. 

There  are  other  Hydroids  giving  rise  to  Me- 
dusae buds,  from  which,  however,  the  Medusae 
do  not  separate  to  begin  a  new  life,  but  wither 
on  the  Hydroid  stock,  after  having  come  to  ma- 
turity and  dropped  their  eggs.  Such  is  the  Hy- 
dr actinia  polyclina.  This  curious  community 
begins,  like  the  preceding  ones,  with  a  single 


ALTERNATE  GENERATIONS.        257 

little  individual,  settling  upon  some  shell  or 
stone,  or  on  the  rocks  in  a  tide-pool,  where  it 
will  sometimes  cover  a  space  of  several  square 
feet.  Rosy  in  color,  very  soft  and  delicate  in 
texture,  such  a  growth  of  Hydractinia  spreads 
a  velvet-like  carpet  over  the  rocks  on  which  it 
occurs.  They  may  be  kept  in  aquariums  with 
perfect  success,  and  for  that  purpose  it  is  better 
to  gather  them  on  single  shells  or  stones,  so 
that  the  whole  community  may  be  removed  un- 
broken. These  colonies  of  Hydractinia  have  one 
very  singular  character:  they  exist  in  distinct 
communities,  some  of  which  give  birth  only  to 
male,  others  to  female  individuals.  The  func- 
tions, also,  are  divided,  —  certain  members  .of 
the  community  being  appointed  to  special  offices, 
in  which  the  others  do  not  share.  Some  bear 
the  Medusae  buds,  which  in  due  time  become 
laden  with  eggs,  but,  as  I  have  said,  wither  and 
die  after  the  eggs  are  hatched.  Others  put  forth 
Hydroid  buds  only,  while  others  again  are  wholly 
sterile.  About  the  outskirts  of  the  community 
are  more  simple  individuals,  whose  whole  body 
seems  to  be  hardly  more  than  a  double-walled 
tube,  terminating  in  a  knob  of  lasso-cells.  They 
are  like  long  tentacles  placed  where  they  can 
most  easily  seize  the  prey  that  happens  to  ap- 
proach the  little  colony.  The  entire  community 
is  connected  at  its  base  by  a  horny  net-work, 

Q 


258 


ALTERNATE   GENERATIONS. 


uniting  all  the  Hydroid  stems  in  its  meshes, 
and  spreading  over  the  whole  surface  on  which 
the  colony  has  established  itself. 


Hydractinia  polyclina  :  a,  sterile  individual  5  &,  fertile  individual,  producing 
female  Medusae  ;  dy  e,  female  Medusee,  containing  advanced  eggs  ;  /,  gr,  A,  i, 
cluster  of  female  Medusas,  with  less  advanced  eggs  ;  o,  peduncle  of  mouth, 
with  short  globular  tentacles  ;  c,  individual  with  globular  tentacles,  upon 
which  no  Medusas  have  appeared,  or  from  which  they  have  dropped. 

There  is  a  very  curious  and  beautiful  animal, 
or  rather  community  of  animals,  closely  allied 
to  the  Hydractinia  polyclina,  which  next  de- 
serves to  be  noticed.  The  Portuguese  Man-of- 
War  —  so  called  from  its  bright-colored  crest, 
which  makes  it  so  conspicuous  as  it  sails  upon 
the  water,  and  the  long  and  various  streamers 
that  hang  from  its  lower  side  —  is  such  a  com- 
munity of  animals  as  I  have  just  described,  re- 
versed in  position,  however,  with  the  individuals 
hanging  down,  and  the  base  swollen  and  ex- 
panded to  make  the  air-bladder  which  forms  its 


ALTERNATE  GENERATIONS. 


259 


brilliant  crested  float.  In  this  curious  Acale- 
phian  Hydroid,  or  Physalia,  the  individuality  of 
function  is  even  more  marked  than  in  the  Hy- 


Physalia,  or  Portuguese  Man-of-War. 

dractinia.     As   in  the  latter,  some  of  the  indi- 
viduals are  Medusae-bearing,  and  others  simple 


260        ALTERNATE  GENERATIONS. 

Hydras  ;  but,  beside  these,  there  are  certain  mem- 
bers of  the  community  who  act  as  swimmers,  to 
carry  it  along  through  the  water,  —  others  that 
are  its  purveyors,  catching  the  prey,  by  which, 
however,  they  profit  only  indirectly,  for  others 
are  appointed  to  eat  it,  and  these  feeders  may 
be  seen  sometimes  actually  gorged  with  the  food 
they  have  devoured,  and  which  is  then  distrib- 
uted throughout  the  community  by  the  process 
of  digestion  and  circulation. 

It  would  be  hopeless,  even  were  it  desirable, 
to  attempt  within  the  limits  of  such  an  article 
as  this  to  give  the  faintest  idea  of  the  number 
and  variety  of  these  Hydroids ;  and  I  will  there- 
fore say  nothing  of  the  endless  host  of  Tubula- 
rians,  Campanularians,  Sertularians,  etc.  They 
are  very  abundant  along  our  coast,  and  will  well 
reward  any  one  who  cares  to  study  their  habits 
and  their  singular  modes  of  growth.  For  their 
beauty,  simply,  it  is  worth  while  to  examine 
them.  Some  are  deep  red,  others  rosy,  others 
purple,  others  white  with  a  glitter  upon  them, 
as  if  frosted  with  silver.  Their  homes  are  very 
various.  Some  like  the  fresh,  deep  sea-water, 
while  they  avoid  the  dash  and  tumult  of  the 
waves ;  and  they  establish  themselves  in  the  de- 
pressions on  some  low  ledge  of  rocks  running 
far  out  from  the  shore,  and  yet  left  bare  for 
an  hour  or  two,  when  the  tide  is  out.  In  such 


ALTERNATE  GENERATIONS.        261 

a  depression,  forming  a  stony  cup  filled  with 
purest  sea-water,  and  overhung  by  a  roof  of  rock, 
which  may  be  fringed  by  a  heavy  curtain  of 
brown  sea-weed,  the  rosy-headed,  branching  Eu- 
dendrium,  one  of  the  prettiest  of  the  Tubula- 
rians,  may  be  found.  Others  choose  the  tide- 
pools,  higher  up  on  the  rocks,  that  are  freshened 
by  the  waves  only  when  the  tide  is  full :  such  are 
the  small,  creeping  Campanularians.  Others, 
again,  like  the  tiny  Dynamena,  prefer  the  rougher 
action  of  the  sea;  and  they  settle  upon  the 
sides  of  rents  and  fissures  in  the  cliffs  along  the 
shore,  where  even  in  calm  weather  the  waves 
rush  in  and  out  with  a  certain  degree  of  violence, 
broken  into  eddies  by  the  abrupt  character  of 
the  rocks.  Others  seek  the  broad  fronds  of  the 
larger  sea-weeds,  and  are  lashed  up  and  down 
upon  their  spreading  branches,  as  they  rock  to 
and  fro  with  the  motion  of  the  sea.  Many  live 
in  sheltered  harbors,  attaching  themselves  to 
floating  logs,  or  to  the  keels  of  vessels ;  and  some 
are  even  so  indifferent  to  the  freshness  of  the 
water  that  they  may  be  found  in  numbers  along 
the  city-wharves.* 

Beside  the  Jelly-Fishes  arising  from  Hydroids, 

*  Those  who  care  to  know  more  of  the  habits  and  structure  of 
these  animals  will  find  detailed  descriptions  of  all  the  various  species 
of  our  coast,  illustrated  by  numerous  plates,  in  the  fourth  volume  of 
my  Contributions  to  the  Natural  History  of  the  United  States,  pub- 
lished some  time  ago. 


262        ALTERNATE  GENERATIONS. 

there  are  many  others  resembling  these  in  all 
the  essential  features  of  their  structure,  but  dif- 
fering in  their  mode  of  development ;  for,  al- 
though more  or  less  Polyp-like  when  first  born 
from  the  egg,  they  never  become  attached,  nor 
do  they  ever  bud  or  divide,  but  reach  their  mature 
condition  without  any  such  striking  metamor- 
phoses as  those  that  characterize  the  develop- 
ment of  the  Hydroid  Acalephs.  All  the  Medusa, 
whether  they  arise  from  buds  on  the  Hydroid 
stock,  like  the  Sarsia,  or  from  transverse  division 
of  the  Hydroid  form,  like  the  Aurelia,  or  grow 
directly  from  the  egg  to  maturity,  without  paus- 
ing in  the  Hydroid  phase,  like  the  Campanella, 
agree  in  the  general  division  and  relation  of 
parts.  All  have  a  central  cavity,  from  which 
arise  radiating  tubes  extending  to  the  margin 
of  the  umbrella-like  disk,  where  they  unite  either 
in  a  net-work  of  meshes  or  in  a  single  circular 
tube.  But  there  is  a  great  difference  in  the 
oral  apparatus ;  the  elaborate  ruffled  curtains, 
that  hang  from  the  corners  of  the  mouth,  occur 
only  in  the  Species  arising  from  the  transverse 
division  of  the  Polyp-like  young.  For  this  rea- 
son they  are  divided  into  two  Orders,  —  the  Hy- 
droids  and  the  Discophorae. 

The  third  order,  the  Ctenophoras,  are  among 
the  most  beautiful  of  the  Acalephs.  I  have  spo- 
ken of  the  various  hues  they  assume  when  in 


ALTERNATE  GENERATIONS. 


263 


motion,  and  I  will  add  one  word  of  the  peculiar- 
ity in  their  structure  which  causes  this  effect. 
The  Ctenophorae  differ  from  the  Jelly-Fishes  de- 
scribed above  in  sending  off  from  the  main  cavity 
only  two  main  tubes,  instead  of  four  like  the 
others  ;  but  each  of  these  tubes  divides  and  sub- 
divides in  four  branches  as  it  approaches  the  pe- 
riphery. From  the  eight  branches  produced  in 
this  way  there  arise  vertical  tubes  extending  in 


Idyia  roseola  5  one  of  our  Ctenophorae  :   a,  anal  aperture  ;  ft,  radiating  tube  ; 
c,  circular  tube  ;  d,  e,f,  gr,  h,  rows  of  locomotive  fringes. 

opposite  directions  up  and  down  the  sides  of 
the  body.  Along  these  vertical  tubes  run  the 
rows  of  little  locomotive  oars,  or  combs,  as  they 
have  been  called,  from  which  these  animals  derive 
their  name  of  Ctenophorae.  The  rapid  motion 
of  these  flappers  causes  the  decomposition  of  the 
rays  of  light  along  the  surface  of  the  body,  pro- 
ducing the  most  striking  prismatic  effect ;  and  it 
is  no  exaggeration  to  say  that  no  jewel  is  brighter 


264        ALTERNATE  GENERATIONS. 

than  these  Ctenophorae  as  they  move  through  the 
water.* 

I  trust  I  have  succeeded  in  showing  that  the 
three  Orders  of  the  Acalephs  are,  like  the  five 
Orders  of  the  Echinoderms,  different  degrees  of 
complication  of  the  same  structure.  In  the  Hy- 
droids,  the  organization  does  not  rise  above  the 
simple  digestive  cavity  enclosed  by  the  double 
body-wall ;  and  we  might  not  suspect  their  rela- 
tion to  the  Acalephs,  did  we  not  see  the  Jelly- 
Fish  born  from  the  Hydroid  stock.  In  the  Hy- 
droid-Medusae  and  Discophorae,  instead  of  a  sim- 
ple digestive  sac,  as  in  the  Hydroids,  we  have  a 
cavity  sending  off  tubes  toward  the  periphery, 
which  ramify  more  or  less  in  their  course.  Now 
whether  there  are  four  tubes  or  eight,  whether 
they  ramify  extensively  or  not,  whether  there  are 
more  or  less  complicated  appendages  around  the 
margin  or  the  mouth,  makes  no  difference  in  the 
essential  structure  of  these  bodies.  They  are  all 
disk-like  in  outline,  they  all  have  tentacles  hang- 
ing from  the  margin,  and  a  central  cavity  from 
which  tubes  diverge  that  divide  the  body  into  a 
certain  number  of  segments,  bearing  in  all  the 
same  relation  to  each  other  and  to  the  central 
cavity.  In  the  Ctenophorae,  another  complication 
of  structure  is  introduced  in  the  combination  of 

*  For  more  details  concerning  the  Ctenophorce,  see  the  third 
volume  of  my  Contributions. 


ALTERNATE  GENERATIONS.        265 

vertical  with  horizontal  tubes  and  the  external 
appendages  accompanying  them. 

But,  whatever  their  differences  may  be,  a  very 
slight  effort  of  the  imagination  only  is  needed  to 
transform  any  one  of  these  forms  into  any  other. 
Reverse  the  position  of  any  simple  Hydra,  so  that 
the  tentacles  hang  down  from  the  margin,  and 
let  four  tubes  radiate  from  the  central  cavity  to 
the  periphery,  and  we  have /the  lowest  form  of 
Jelly-Fish.  Expand  the  cup  of  the  Hydra  to 
form  a  gelatinous  disk,  increase  the  number  of 
tubes,  complicate  their  ramifications,  let  eyes 
be  developed  along  the  margin,  add  some  exter- 
nal appendages,  and  we  have  the  Discophore. 
Elongate  the  disk  in  order  to  give  the  body  an 
oval  form,  diminish  the  number  of  main  tubes, 
and  let  them  give  off  vertical  as  well  as  horizontal 
branches,  and  we  have  the  Ctenophore. 

In  the  Class  of  Polyps  there  are  but  two  Or- 
ders, —  the  Actinoids  and  the  Halcyonoids  ;  and 
I  have  already  said  so  much  of  the  structure  of 
Polyps  that  I  think  I  need  not  repeat  my  remarks 
here  in  order  to  show  the  relation  between  these 
groups.  The  body  of  all  Polyps  consists  of  a 
sac  divided  into  chambers  by  vertical  partitions, 
and  having  a  wreath  of  hollow  tentacles  around 
the  summit,  each  one  of  which  opens  into  one  of 
the  chambers.  The  greater  complication  of  these 
parts  and  their  limitation  in  definite  numbers 
12 


266        ALTERNATE  GENERATIONS. 

constitute  the  characters  upon  which  their  supe- 
riority or  inferiority  of  structure  is  based.  Here 
the  comparison  is  easily  made  ;  it  is  simply  the 
complication  and  number  of  identical  parts  that 
make  the  difference  between  the  Orders.  The 
Actinoids  stand  lowest  from  the  simple  character 
and  indefinite  increase  of  these  parts  ;  while  the 
Halcyonoids,  with  their  eight  lobed  tentacles, 
corresponding  to  the  same  number  of  internal 
divisions,  are  placed  above  them. 

In  the  name  of  the  division  to  which  they  all 
belong  we  have  the  key-note  to  the  common 
structure  of  the  three  Classes  whose  Orders  we 
have  been  comparing :  they  are  Radiates.  The 
idea  of  radiation  lies  at  the  foundation  of  all  these 
animals,  whatever  be  their  form  or  substance. 
Whether  stony,  like  the  Corals,  or  soft,  like  the 
Sea-Anemone,  or  gelatinous  and  transparent,  like 
the  Jelly-Fish,  or  hard  and  brittle,  like  the  Sea- 
Urchins,  —  whether  round  or  oblong  or  cylin- 
drical or  stellate,  their  internal  structure  always 
obeys  this  law  of  radiation. 

Not  only  is  this  true  in  a  general  way,  but  the 
comparison  may  be  traced  in  all  the  details. 
One  may  ask  how  the  narrow  radiating  tubes  of 
the  Acalephs,  traversing  the  gelatinous  mass  of 
the  body,  can  be  compared  to  the  wide  radiating 
chambers  of  the  Polyp  ;  and  yet  nothing  is  more 
simple  than  to  thicken  the  partitions  in  the 


ALTERNATE  GENERATIONS.        267 

Polyps  so  much  as  to  contract  the  chambers 
between  them,  till  they  form  narrow  alleys  in- 
stead of  wide  spaces,  and  then  we  have  the  tubes 
of  the  Jelly-Fish.  In  the  Jelly-Fish  there  is  a 
circular  tube  around  the  margin,  into  which  all 
the  radiating  tubes  open.  What  have  we  to 
compare  with  this  in  the  Polyps  ?  The  outer 
edge  of  each  partition  in  the  Polyp  is  pierced  by 
a  hole  near  the  margin.  Of  course  when  the 
partition  is  thickened,  this  hole,  remaining  open, 
becomes  a  tube ;  for  what  is  a  tube  but  an 
elongated  hole  ?  The  comparison  of  the  Aca- 
lephs  with  the  Echinoderms  is  still  easier,  for 
they  both  have  tubes  ;  but  in  the  latter  the  tubes 
are  enclosed  in  walls  of  their  own,  instead  of 
traversing  the  mass  of  the  body,  as  in  Aca- 
lephs,  etc. 

In  preparing  these  chapters  on  the  homologies 
of  Radiates,  I  have  felt  the  difficulty  of  divesting 
my  subject  of  the  technicalities  which  cling  to  all 
scientific  results,  until  they  are  woven  into  the 
tissue  of  our  every-day  knowledge  and  assume 
the  familiar  garb  of  our  common  intellectual 
property.  When  the  forms  of  animals  are  as 
familiar  to  children  as  their  ABC,  and  the 
intelligent  study  of  Natural  History,  from  the 
objects  themselves,  and  not  from  text-books 
alone,  is  introduced  into  all  our  schools,  we 


268        ALTERNATE  GENERATIONS. 

shall  have  popular  names  for  things  that  can 
now  only  be  approached  with  a  certain  profes- 
sional stateliness  on  account  of  their  technical 
nomenclature.  The  best  result  of  such  familiar- 
ity with  Nature  will  be  the  recognition  of  an 
intellectual  unity  holding  together  all  the  vari- 
ous forms  of  life  as  parts  of  one  Creative  Con- 
ception. 


THE   OVARIAN  EGG.  269 


CHAPTER   XV. 

THE   OVARIAN  EGG. 

ALL  important  changes  in  the  social  and  politi- 
cal condition  of  man,  whether  brought  about  by 
violent  convulsions  or  effected  gradually,  are  at 
once  recognized  as  eras  in  the  history  of  human- 
ity. But  on  the  broad  high-road  of  civilization 
along  which  men  are  ever  marching,  they  pass  by 
unnoticed  the  landmarks  of 'intellectual  progress, 
unless  they  chance  to  have  some  direct  bearing 
on  what  is  called  the  practical  side  of  life.  Such 
an  era  marked  the  early  part  of  our  own  century  ; 
and  though  at  the  time  a  thousand  events  seemed 
more  full-freighted  for  the  world  than  the  dis- 
covery of  some  old  bones  in  the  quarries  of  Mont- 
martre,  and  though  many  a  man  seemed  greater 
in  the  estimation  of  the  hour  than  the  professor 
at  the  Jardin  des  Plantes  who  strove  to  reconstruct 
these  fragments,  yet  the  story  that  they  told 
lighted  up  all  the  past,  and  showed  its  true  con- 
nection with  the  present. 

Before  the  year  1800,  men  had  never  suspected 
that  their  home  had  been  tenanted  in  past  times 


270  THE   OVARIAN  EGG. 

by  a  set  of  beings  totally  different  from  those 
that  inhabit  it  now ;  still  farther  was  it  from  their 
thought  to  imagine  that  creation  after  creation 
had  followed  each  other  in  successive  ages,  every 
one  stamped  with  a  character  peculiarly  its  own. 
It  was  Cuvier  who,  aroused  to  new  labors  by  the 
hint  he  received  from  the  bones  unearthed  at 
Montmartre,  to  which  all  his  vast  knowledge  of 
living  animals  gave  him  no  clew,  established  by 
means  of  most  laborious  investigations  the  as- 
tounding conclusion,  that,  prior  to  the  existence 
of  the  animals  and  plants  now  living,  this  globe 
had  been  the  theatre  of  another  set  of  beings, 
every  trace  of  which  had  vanished  from  the  face 
of  the  earth.  To  his  alert  and  active  intellect, 
and  powerful  imagination,  a  word  spoken  out  of 
the  past  was  pregnant  with  meaning ;  and  when 
he  had  once  convinced  himself  that  he  had  found 
a  single  animal  that  had  no  counterpart  among 
living  beings,  it  gave  him  the  key  to  many  mys- 
teries. The  existence  of  a  past  creation  once 
suggested,  confirmation  was  found  in  a  thousand 
facts  overlooked  before.  The  solid  crust  of  the 
earth  gave  up  its  'dead,  and  from  the  snows  of 
Siberia,  from  the  soil  of  Italy,  from  caves  of  Cen- 
tral Europe,  from  mines,  from  the  rent  sides  of 
mountains  and  from  their  highest  peaks,  from 
the  coral  beds  of  ancient  oceans,  the  varied  ani- 
mals that  had  possessed  the  earth,  ages  before 
man  was  created,  spoke  to  us  of  the  past. 


THE   OVARIAN  EGG.  271 

No  sooner  were  these  facts  established,  than 
the  relation  between  the  extinct  world  and  the 
world  of  to-day  became  the  subject  of  extensive 
researches  and  comparisons ;  innumerable  theo- 
ries were  started  to  account  for  the  differences, 
and  to  determine  the  periods  and  manner  of  the 
change  ;  and  the  science  of  Paleontology  became 
one  of  the  most  important  departments  of  inves- 
tigation in  modern  times.  It  is  not  my  intention 
to  enter  now  at  any  length  upon  the  subject  of 
geological  succession,  though  I  hope  to  return  to 
it  hereafter  in  a  series  of  papers  upon  that  and 
kindred  topics  ;  but  I  allude  to  it  here,  before 
presenting  some  views  upon  the  maintenance  of 
organic  types  as  they  exist  in  our  own  period,  for 
the  following  reason.  Since  it  has  been  shown 
that  from  the  beginning  of  Creation  till  the  pres- 
ent time  the  physical  history  of  the  world  has 
been  divided  into  a  succession  of  distinct  periods, 
each  one  accompanied  by  its  characteristic  ani- 
mals and  plants,  so  that  our  own  epoch  is  only 
the  closing  one  in  a  long  procession  of  ages, 
naturalists  have  been  constantly  striving  to  find 
the  connecting  link  between  them  all,  and  to 
prove  that  each  such  creation  has  been  a  normal 
and  natural  growth  out  of  the  preceding  one. 
With  this  aim  they  have  tried  to  adapt  the  phe- 
nomena of  reproduction  among  animals  to  the 
problem  of  creation,  and  to  make  the  beginning 


272  THE   OVARIAN  EGG. 

of  life  in  the  individual  solve  that  great  mystery 
of  the  beginning  of  life  in  the  world.  In  other 
words,  they  have  endeavored  to  show  that  the 
fact  of  successive  generations  is  analogous  to  that 
of  successive  creations,  and  that  the  processes  by 
which  animals,  once  created,  are  maintained  un- 
changed during  the  period  to  which  they  belong, 
will  account  also  for  their  primitive  existence. 

I  wish,  at  the  outset,  to  forestall  any  such  mis- 
application of  the  facts  I  am  about  to  state,  and 
to  impress  upon  my  readers  the  difference  between 
these  two  subjects  of  inquiry,  since  it  by  no  means 
follows,  that,  because  individuals  are  endowed 
with  the  power  of  reproducing  and  perpetuating 
their  kind,  they  are  in  any  sense  self-originating. 
Still  less  probable  does  this  appear,  when  we  con- 
sider, that,  since  man  has  existed  upon  the  earth, 
no  appreciable  change  has  taken  place  in  the  ani- 
mal or  vegetable  world  ;  and  so  far  as  our  knowl- 
edge goes,  this  would  seem  to  be  equally  true  of 
all  the  periods  preceding  ours,  each  one  maintain- 
ing unbroken  to  its  close  the  organic  character 
impressed  upon  it  at  the  beginning. 

The  question  I  propose  to  consider  here  is 
simply  the  mode  by  which  organic  types  are  pre- 
served as  they  exist  at  present.  Every  one  has  a 
summary  answer  to  this  question  in  the  state- 
ment that  all  these  short-lived  individuals  repro- 
duce themselves,  and  thus  maintain  their  kinds. 


THE   OVARIAN  EGG.  273 

But  the  modes  of  reproduction  are  so  varied, 
the  changes  some  animals  undergo  during  their 
growth  so  extraordinary,  the  phenomena  accom- 
panying these  changes  so  startling,  that,  in  the 
pursuit  of  the  subject,  a  new  and  independent 
science  —  that  of  Embryology  —  has  grown  up, 
of  the  utmost  importance  in  the  present  state  of 
our  knowledge. 

The  prevalent  ideas  respecting  the  reproduction 
of  animals  are  made  up  from  the  daily  observation 
of  those  immediately  about  us,  in  the  barn-yard 
and  on  the  farm.  But  the  phenomena  here  are 
comparatively  simple  and  easily  traced.  The  mo- 
ment, however,  we  extend  our  observations  beyond 
our  cattle  and  fowls,  and  enter  upon  a  wider  field 
of  investigation,  we  are  met  by  the  most  startling 
facts.  Not  the  least  baffling  of  these  are  the  dis- 
proportionate numbers  of  males  and  females  in 
certain  kinds  of  animals,  their  unequal  develop- 
ment, as  well  as  the  extraordinary  difference  be- 
tween the  sexes  among  certain  species,  so  that 
they  seem  as  distinct  from  each  other  as  if  they 
belonged  to  separate  groups  of  the  Animal  King- 
dom. We  have  close  at  hand  one  of  the  most 
striking  instances  of  disproportionate  numbers  in 
the  household  of  the  Bee,  with  its  one  fertile  fe- 
male charged  with  the  perpetuation  of  the  whole 
community,  while  her  innumerable  sterile  sister- 
hood, amid  a  few  hundred  drones,  contribute  to 

12*  K 


274  THE   OVARIAN  EGG. 

its  support  iii  other  ways.  Another  most  inter- 
esting chapter  connected  with  the  maintenance  of 
animals  is  found  in  the  various  methods  and  dif- 
ferent degrees  of  care  with  which  they  provide  for 
their  progeny  :  some  having  fulfilled  their  whole 
duty  toward  their  offspring  when  they  have  given 
them  birth,  while  others  seek  hiding-places  for 
the  eggs  they  have  laid,  and  watch  with  a  certain 
care  over  their  development,  and  still  others  feed 
their  young  till  they  can  provide  for  themselves, 
or  build  nests,  or  burrow  holes  in  the  ground,  or 
construct  earth  mounds  for  their  shelter,  and  by 
a  variety  of  means  secure  them  from  possible 
dangers. 

But,  whatever  be  the  difference  in  the  outward 
appearance  or  the  habits  of  animals,  one  thing  is 
common  to  them  all  without  exception  :  at  some 
period  of  their  lives  they  produce  eggs,  which, 
being  fertilized,  give  rise  to  beings  of  the  same 
kind  as  the  parent.  This  mode  of  generation  is 
universal,  and  is  based  upon  that  harmonious 
antagonism  between  the  sexes,  that  contrast  be- 
tween the  male  and  the  female  element,  that  at 
once  divides  and  unites  the  whole  Animal  King- 
dom. And  although  this  exchange  of  influence 
is  not  kept  up  by  an  equality  of  numeric  relations, 
—  since  not  only  are  the  sexes  very  unequally 
divided  in  some  kinds  of  animals,  but  the  male 
and  female  elements  are  even  combined  in  cer- 


THE   OVARIAN  EGG.  275 

tain  types,  so  that  the  individuals  are  uniformly 
hermaphrodites,  —  yet  I  firmly  believe  that  this 
numerical  distribution,  however  unequal  it  may 
seem  to  us,  is  not  without  its  ordained  accuracy 
and  balance.  He  who  has  assigned  its  place  to 
every  leaf  in  the  thickest  forest,  according  to  an 
arithmetical  law  which  prescribes  to  each  its  al- 
lotted share  of  room  on  the  branch  where  it  grows, 
will  not  have  distributed  animal  life  with  less 
care  and  regularity. 

Although  reproduction  by  eggs  is  common  to 
all  animals,  it  is  only  one  among  several  modes 
of  multiplication.  We  have  seen  that  certain 
animals,  besides  the  ordinary  process  of  genera- 
tion, also  increase  their  numbers  naturally  and 
constantly  by  self-division,  so  that  out  of  one  in- 
dividual many  individuals  may  arise  by  a  natural 
breaking  up  of  the  whole  body  into  distinct  sur- 
viving parts.  This  process  of  normal  self-division 
may  take  place  at  all  periods  of  life  :  it  may  form 
an  early  phase  of  metamorphosis,  as  in  the  Hy- 
droid  of  our  common  Aurelia,  described  in  the 
last  article ;  or  it  may  even  take  place  before  the 
young  is  formed  in  the  egg.  In  such  a  case,  the 
egg  itself  divides  into  a  number  of  portions,  — 
two,  four,  eight,  or  even  twelve  and  sixteen  in- 
dividuals being  normally  developed  from  every 
egg,  in  consequence  of  this  singular  process  of 
segmentation  of  the  yolk,  which  takes  place, 


276  THE   OVARIAN  EGG. 

indeed,  in  all  eggs,  but  in  those  which  produce 
but  one  individual  is  only  a  stage  in  the  natural 
growth  of  the  yolk  during  its  transformation  into 
a  young  embryo.  As  the  facts  here  alluded  to 
are  not  very  familiar,  even  to  professional  natural- 
ists, I  may  be  permitted  to  describe  them  more 
in  detail. 

No  one  who  has  often  walked  across  a  sand- 
beach  in  summer  can  have  failed  to  remark  what 
the  children  call  "  sand  saucers."  The  name  is 
not  a  bad  one,  with  the  exception  that  the  saucer 
lacks  a  bottom ;  but  the  form  of  these  circular 
bands  of  sand  is  certainly  very  like  a  saucer  with 
the  bottom  knocked  out.  Hold  one  of  them 
against  the  light  and  you  will  see  that  it  is  com- 
posed of  countless  transparent  spheres,  each  of 
the  size  of  a  small  pin's  head.  These  are  the 
eggs  of  our  common  Natica  or  Sea-Snail.  Any 
one  who  remembers  the  outline  of  this  shell  will 
easily  understand  the  process  by  which  its  eggs 
are  left  lying  on  the ,  beach  in  the  form  I  have 
described.  They  are  laid  in  the  shape  of  a  broad, 
short  ribbon,  pressed  between  the  mantle  of  the 
animal  and  its  shell,  and,  passing  out,  they  cover 
the  exterior  of  the  shell,  over  which  they  are 
rolled  up,  with  a  kind  of  glutinous  envelope,  — 
for  the  eggs  are  held  together  by  a  soft  gluti- 
nous substance.  Thus  surrounded,  the  Natica, 
whose  habit  is  to  burrow  under  the  surface  of 


THE   OVARIAN  EGG.  277 

the  beach,  soon  covers  itself  with  sand,  the  par- 
ticles of  which,  in  contact  with  the  glutinous 
substance  of  the  eggs,  quickly  form  a  cement 
that  binds  the  whole  together  in  a  kind  of  paste. 
When  consolidated,  it  drops  off  from  the  shell, 
having  taken  the  mould  of  its  form,  as  it  were, 
and  retaining  the  curve  which  distinguishes  the 
outline  of  the  Natica.  Although  these  saucers 
look  perfectly  round,  it  will  be  found  that  the 
edges  are  not  soldered  together,  but  are  simply 
lapped  one  over  the  other.  Every  one  of  the 
thousand  little  spheres  crowded  into  such  a  circle 
of  sand  contains  an  egg.  If  we  follow  the  develop- 
ment of  these  eggs,  we  shall  presently  find  that 
each  one  divides  into  two  halves,  these  again 
dividing  to  make  four  portions,  then  the  four 
breaking  up  into  eight,  and  so  on,  till  we  may 
have  the  yolks  divided  into  no  less  than  sixteen 
distinct  parts.  Thus  far  this  process  of  segmen- 
tation is  similar  to  that  of  the  egg  in  other  ani- 
mals ;  but,  as  we  shall  see  hereafter,  the  regular 
segmentation  of  an  egg  seems  usually  to  re- 
sult only  in  a  change  in  the  quality  of  its  sub- 
stance, for  the  portions  coalesce  again  to  form 
one  mass,  from  which  a  new  individual  is  finally 
sketched  out,  as  a  simple  embryo  at  first,  but 
gradually  undergoing  all  the  changes  peculiar 
to  its  kind,  till  a  new-born  animal  escapes  from 
the  egg.  In  the  case  of  the  Natica,  however,  this 


278  THE   OVARIAN  EGG. 

regular  segmentation  changes  its  character,  and 
at  a  certain  period,  in  a  more  or  less  advanced 
stage  of  the  segmentation,  according  to  the  species, 
each  portion  of  the  yolk  assumes  an  individuality 
of  its  own,  and,  instead  of  uniting  again  with  the 
rest,  begins  to  subdivide  for  itself.  In  our  Natica 
heros,  for  instance,  the  common  large  gray  Sea- 
Snail  of  our  coast,  this  change  takes  place  when 
the  yolk  has  subdivided  into  eight  or  sixteen 
parts.  At  that  time  each  portion  begins  a  life  of 
its  own,  not  reuniting  with  its  twin  portions  ;  so 
that  in  the  end,  instead  of  a  single  embryo  grow- 
ing out  of  this  yolk,  we  have  from  eight  to  six- 
teen embryos  arising  from  a  single  yolk,  each 
one  of  which  undergoes  a  series  of  develop- 
ments similar  in  all  respects  to  that  by  which 
a  single  embryo  is  formed  from  each  egg  in 
other  animals.  We  have  other  Naticas  in  which 
the  normal  number  is  twelve;  others,  again,  in 
which  no  less  than  thirty-two  individuals  arise 
from  one  yolk.  But  'this  process  of  segmenta- 
tion, though  in  these  animals  it  leads  to  such  a 
multiplication  of  individuals,  is  exactly  the  same 
as  that  discovered  by  K.  E.  von  Baer  in  the  egg 
of  the  Frog,  and  described  and  figured  by  Pro- 
fessor Bischoff  in  the  egg  of  the  Rabbit,  the  Dog, 
the  Guinea-Pig,  and  the  Deer ;  while  other  em- 
bryologists  have  traced  the  same  process  in  Birds, 
Reptiles,  and  Fishes,  as  well  as  in  a  variety  of 
Articulates,  Mollusks,  and  Radiates. 


THE    OVARIAN   EGG.  279 

Multiplication  by  division  occurs  also  normally 
in  adult  animals  that  have  completed  their  growth. 
This  is  especially  frequent  among  Worms ;  and 
strange  to  say,  there  are  species  in  this  Class 
which  never  lay  eggs  before  they  have  already 
multiplied  themselves  by  self-division. 

Another  mode  of  increase  is  that  by  budding, 
as  in  the  Corals  and  many  other  Radiates.  The 
most  common  instance  of  budding  we  do  not, 
however,  generally  associate  with  this  mode  of 
multiplication  in  the  Animal  Kingdom,  because 
we  are  so  little  accustomed  to  compare  and  gen- 
eralize upon  phenomena  which  we  do  not  see  to 
be  directly  connected  with  one  another.  I  allude 
here  to  the  budding  of  trees,  which  year  after 
year  enlarge  by  the  addition  of  new  individuals 
arising  from  buds.  It  must  be  remembered  here 
that  I  use  the  word  individual  simply  in  its  scien- 
tific sense,  as  designating  singleness  of  existence, 
and  I  trust  that  its  usual  acceptation  will  not 
prevent  a  correct  appreciation  of  the  true  re- 
lation of  buds  to  their  parents  and  to  the  beings 
arising  from  them.  All  buds  have  the  same 
organic  significance,  whether  they  drop  from  the 
parent  stock  to  become  distinct  individuals  in  the 
common  acceptation  of  the  term,  or  remain  con- 
nected with  the  parent  stock,  as  in  Corals  and  in 
trees,  thus  forming  growing  communities  of  com- 
bined individuals.  Nor  will  it  matter  much  in 


280  THE   OVARIAN  EGG. 

connection  with  the  subject  under  discussion, 
whether  these  buds  start  from  the  surface  of  an 
animal  or  sprout  in  its  interior,  to  be  cast  off  in 
due  time.  Neither  is  the  inequality  of  buds, 
varying  more  or  less  among  themselves,  any 
sound  reason  for  overlooking  their  essential  iden- 
tity of  structure.  We  have  seen  instances  of  this 
among  Acalephs,  and  it  is  still  more  apparent 
among  trees  which  produce  simultaneously  leaf 
and  flower  buds,  and  even  separate  male  and 
female  flower-buds,  as  is  the  case  with  our  Hazels, 
Oaks,  etc. 

It  is  not,  however,  my  purpose  here  to  de- 
scribe the  various  modes  of  reproduction  and 
multiplication  among  animals  and  plants,  nor  to 
discuss  the  merits  of  the  different  opinions  re- 
specting their  numeric  increase,  according  to 
which  some  persons  hold  that  all  types  originated 
from  a  few  primitive  individuals,  while  others 
believe  that  the  very 'numbers  now  in  existence 
are  part  of  the  primitive  plan,  and  essential  to 
the  harmonious  relations  existing  between  the 
animal  and  vegetable  world.  I  would  only  at- 
tempt to  show  that  in  the  plan  of  Creation  the 
maintenance  of  types  has  been  secured  through 
a  variety  of  means,  but  under  such  limitations, 
that,  within  a  narrow  range  of  individual  differ- 
ences, all  representatives  of  one  kind  of  animals 
agree  with  one  another,  whether  derived  frqm 


THE   OVARIAN  EGG.  281. 

eggs,  or  produced  by  natural  division,  or  by 
budding ;  and  that  the  constancy  of  these  normal 
processes  of  reproduction,  as  well  as  the  uni- 
formity of  their  results,  precludes  the  idea  that 
the  specific  differences  among  animals  have  been 
produced  by  the  very  means  that  secure  their 
permanence  of  type.  The  statement  itself  im- 
plies a  contradiction,  for  it  assumes  that  the  same 
influences  prevent  and  produce  changes  in  the 
condition  of  the  Animal  Kingdom.  Facts  are  all 
against  such  an  assumption ;  there  is  not  a  fact 
known  to  science  tending  to  show  that  any  being, 
in  the  natural  process  of  reproduction  and  multi- 
plication, has  ever  diverged  from  the  course  nat- 
ural to  its  kind,  or  that  a  single  kind  has  ever 
been  transformed  into  any  other.  But  this  once 
established,  and  setting  aside  the  idea  that  Em- 
bryology is  to  explain  to  us  the  origin  as  well 
as  the  maintenance  of  life,  it  yet  has  most  im- 
portant lessons  for  us,  and  the  field  it  covers 
is  constantly  enlarging  as  the  study  is  pursued. 
The  first  and  most  important  result  of  the 
science  of  Embryology  was  one  for  which  the 
scientific  world  was  wholly  unprepared.  Down 
to  our  own  century,  nothing  could  have  been 
farther  from  the  conception  of  anatomists  and 
physiologists  than  the  fact,  now  generally  admit- 
ted, that  all  animals,  without  exception,  arise 
from  eggs.  Though  Linnaeus  had  already  ex- 


282  THE   OVARIAN   EGG. 

pressed  this  great  truth  in  the  sentence  so  often 
quoted,  —  "  Omne  vivum  ex  ovo," —  yet  he  was 
not  himself  aware  of  the  significance  of  his  own 
statement,  for  the  existence  of  the  Mammalian 
egg  was  not  then  dreamed  of.  Since  then  the 
discoveries  of  Von  Baer  and  others  have  shown 
not  only  that  the  production  of  eggs  is  common 
to  all  living  beings  without  exception,  from  the 
lowest  Radiate  to  the  highest  Vertebrate,  but 
that  their  structure  is  at  first  identical  in  all, 
composed  of  the  same  primitive  elements,  and 
undergoing  exactly  the  same  process  of  growth 
up  to  the  time  when  they  assume  the  special 
character  peculiar  to  their  kind.  This  is  un- 
questionably one  of  the  most  comprehensive  gen- 
eralizations of  modern  times. 

In.  common  parlance,  we  understand  by  an 
egg  something  of  the  nature  of  a  hen's  egg,  a 
mass  of  yolk  surrounded  with  white  and  enclosed 
in  a  shell.  But  to  the  naturalist,  the  envelopes 
of  the  egg,  which  vary  greatly  in  different  ani- 
mals, are  mere  accessories,  while  the  true  egg, 
or,  as  it  is  called,  the  ovarian  egg,  with  which  the 
life  of  every  kind  of  living  beings  may  begin,  is 
a  minute  sphere,  uniform  in  appearance  through- 
out the  Animal  Kingdom,  though  its  intimate 
structure  is  hardly  to  be  reached  even  with  the 
highest  powers  of  the  microscope.  Some  account 
of  these  earlier  stages  of  growth  in  the  egg  may 


THE   OVARIAN  EGG.  283 

not  be  uninteresting  to  my  readers.  I  will  take 
the  egg  of  the  Turtle  as  an  illustration,  since 
that  has  been  the  subject  of  my  own  especial 
study ;  but,  as  I  do  not  intend  tcT^arry  my  re- 
marks beyond  the  period  during  which  the  his- 
tory of  all  vertebrate  eggs  is  the  same,  they  may 
be  considered  of  more  general  application. 

It  is  well  known  that  all  organic  structures, 
whether  animal  or  vegetable,  are  composed  of 
cells.  These  cells  consist  of  an  outside  bag  en- 
closing an  inner  sac,  within  which  there  is  a  dot. 
The  outer  bag  is  filled  with  a  more  or  less  trans- 
parent fluid,  and  the  inner  one  generally  with  a 
more  perfectly  transparent  fluid,  while  the  dot 
has  a  dark  appearance.  In  the  language  of  our 
science,  the  outer  envelope  is  called  the  Ecto- 
blast,  the  inner  sac  the  Mesoblast,  and  the  dot 
the  Entoblast.  Although  they  are  peculiarly 
modified  to  suit  the  different  organs,  these  cells 
never  lose  this  peculiar  structure ;  it  may  be 
traced  even  in  the  long  drawn-out  cells  of  the 
flesh,  which  are  like  mere  threads,  but  yet  have, 
at  least  while  forming,  their  outer  and  inner  sac 
and  their  dot. 

In  the  Turtle  the  ovary  is  made  up  of  such 
cells,  spherical  at  first,  but  becoming  hexagonal 
under  pressure,  when  they  are  more  closely 
packed  together.  Between  these  ovarian  cells 
the  egg  originates,  and  is  at  first  a  mere  granule, 


284  THE   OVARIAN  EGG. 

so  minute,  that,  when  placed  under  a  very  high 
magnifying  power,  it  is  but  just  visible.  This 
is  the  incipient  egg,  and  at  this  stage  it  differs 
from  the  surrounding  cells  only  in  being  some- 
what darker,  like  a  drop  of  oil,  and  opaque, 
instead  of  transparent  and  clear  like  the  sur- 
rounding cells.  Under  the  microscope  it  is  found 
to  be  composed  of  two  substances  only :  namely, 
oil  and  albumen.  It  increases  gradually,  arid 
when  it  has  reached  a  size  at  which  it  requires 
to  have  its  diameter  magnified  one  thousand 
times  in  order  to  be  distinctly  visible,  the  outside 
assumes  the  aspect  of  a  membrane  thicker  than 
the  interior  and  forming  a  coating  around  it. 
This  is  owing,  not  to  an  addition  from  outside, 
but  to  a  change  in  the  consistency  of  the  sub- 
stance at  the  surface,  which  becomes  more  closely 
united,  more  compact,  than  the  loose  mass  in  the 
centre.  Presently  we  perceive  a  bright,  lumi- 
nous, transparent  spot  on  the  upper  side  of  the 
egg,  near  the  wall  or  outer  membrane.  This  is 
produced  by  a  concentration  of  the  albumen, 
which  now  separates  from  the  oil  and  collects  at 
the  upper  side  of  the  egg,  forming  this  light  spot, 
called  by  naturalists  the  Purkinjean  vesicle,  after 
its  discoverer,  Purkinje.  When  this  albuminous 
spot  becomes  somewhat  larger,  there  arises  a 
little  dot  in  the  centre,  —  the  germinal  dot,  as  it 
is  called.  And  now  we  have  a  perfect  cell-struc- 


THE   OVARIAN  EGG.  285 

ture,  differing  from  an  ordinary  cell  only  in 
having  the  inner  sac,  enclosing  the  dot,  on  the 
side,  instead  of  in  the  centre.  Thexouter  mem- 
brane corresponds  to  the  .Ectoblast,  orxouter  cell 
sac,  the  Purkinjean  vesicle  to  the  Mesoblast,  or 
inner  cell  sac,  while  the  dot  in  the  centre  an- 
swers to  the  Entoblast.  When  the  Purkinjean 
vesicle  has  completed  its  growth,  it  bursts  and 
disappears ;  but  the  mass  contained  in  it  remains 
in  the  same  region,  and  retains  the  same  char- 
acter, though  no  longer  enclosed  as  before. 

At  a  later  stage  of  the  investigation,  we  see 
why  the  Purkinjean  vesicle,  or  inner  sac  of  the 
egg,  is  placed  on  the  side,  instead  of  being  at 
the  centre,  as  in  the  cell.  It  arises  on  that  side 
along  which  the  axis  of  the  little  Turtle  is  to  lie, 
—  the  opposite  side  being  that  corresponding  to 
the  lower  part  of  the  body.  Thus,  the  lighter, 
more  delicate  part  of  the  substance  of  the  egg 
is  collected  where  the  upper  cavity  of  the  ani- 
mal, enclosing  the  nervous  system  and  brain,  is 
to  be,  while  the  heavy  oily  part  remains  beneath, 
where  the  lower  cavity,  enclosing  all  the  organs 
of  mere  material  animal  existence,  is  afterwards 
developed.  In  other  words,  when  the  egg  is  a 
mere  mass  of  oil  and  albumen,  not  indicating  as 
yet  in  any  way  the  character  of  the  future  ani- 
mal, and  discernible  only  by  the  microscope,  the 
distinction  is  indicated  between  the  brains  and 


286  THE   OVARIAN  EGG. 

the  senses,  between  the  organs  of  instinct  and 
sensation  and  those  of  mere  animal  functions. 
At  that  stage  of  its  existence,  however,  when 
the  egg  consists  of  an  outer  sac,  an  inner  sac, 
and  a  dot,  its  resemblance  to  a  cell  is  unmis- 
takable ;  and,  in  fact,  an  egg,  when  forming,  is 
nothing  but  a  single  cell.  This  comparison  is 
important,  because  there  are  both  animals  and 
plants  which,  during  their  whole  existence,  con- 
sist of  a  single  organic  cell,  while  others  are 
made  up  of  countless  millions  of  such  cells.  Be- 
tween these  two  extremes  we  have  all  degrees, 
from  the  innumerable  cells  that  build  up  the 
body  of  the  highest  Vertebrate  to  the  single- 
celled  Worm,  and  from  the  myriad  cells  of  the 
Oak  to  the  single-celled  Alga. 

But  while  we  recognize  the  identity  of  cell- 
structure  and  egg-structure  at  this  point  in  the 
history  of  the  egg,  we  must  not  forget  the  great 
distinction  between  them,  —  namely,  that  while 
the  cells  remain  component  parts  of  the  whole 
body,  the  egg  separates  itself,  and  assumes  a  dis- 
tinct individual  existence.  Even  now,  while  still 
microscopically  small,  its  individuality  begins. 
Other  substances  collect  around  it,  are  absorbed 
into  it,  nourish  it,  serve  it.  Every  being  is  a 
centre  about  which  many  other  things  cluster 
and  converge,  and  which  has  the  power  to  assimi- 
late to  itself  the  necessary  elements  of  its  life. 


THE   OVAKIAN  EGG.  287 

Every  egg  is  already  such  a  centre,  differing  from 
the  cells  that  surround  it  by  no  material  elements, 
but  by  the  principle  of  life  in  which  its^  individ- 
uality consists,  which  is  to  make  it  a  new  being, 
instead  of  a  fellow-cell  with  those  that  build  up 
the  body  of  the  parent  animal,  and  remain  com- 
ponent parts  of  it.  This  intangible  something  is 
the  subtile  element  that  eludes  our  closest  anal- 
ysis ;  it  is  the  first  indication  of  the  immaterial 
principle  according  to  which  the  new  being  is  to 
develop.  The  physical  germ  we  see ;  the  spirit- 
ual germ  we  cannot  see,  though  we  may  trace  its 
action  on  the  material  elements  through  which  it 
is  expressed. 

The  first  change  in  the  yolk  after  the  formation 
of  the  Purkinjean  vesicle  is  the  appearance  of 
minute  dots  near  the  wall  at  the  side  opposite  the 
vesicle.  These  increase  in  number  and  size,  but 
remain  always  on  that  half  of  the  yolk,  leaving 
the  other  half  of  the  globe  clear.  One  can  hardly 
conceive  the  beauty  of  the  egg  as  seen  through 
the  microscope  at  this  period  of  its  growth,  when 
the  whole  yolk  is  divided,  with  the  dark  granules 
on  one  side;  while  the  other  side,  where  the 
transparent  halo  of  the  vesicle  is  seen,  is  brilliant 
with  light.  With  the  growth  of  the  egg  these 
granules  enlarge,  become  more  distinct,  and  un- 
der the  microscope  some  of  them  appear  to  be 
hollow.  They  are  not  round  in  form,  but  rather 


288  THE   OVARIAN  EGG. 

irregular,  and  under  the  effect  of  light  they  are 
exceedingly  brilliant.  Presently,  instead  of  being 
scattered  equally  over  the  space  they  occupy, 
they  form  clusters,  —  constellations,  as  it  were, 
—  and  between  these  clusters  are  clear  spaces, 
produced  by  the  separation  of  the  albumen  from 
the  oil. 

At  this  period  of  its  growth  there  is  a  wonder- 
ful resemblance  between  the  appearance  of  the 
egg,  as  seen  under  the  microscope,  and  the  fir- 
mament with  the  celestial  bodies.  The  little 
clusters  or  constellations  are  unequally  divided. 
Here  and  there  they  are  two  and  two  like  double 
stars,  or  sometimes  in  threes  or  fives,  or  in  sevens, 
recalling  the  Pleiades  ;  and  the  clear  albuminous 
tracks  between  are  like  the  empty  spaces  separat- 
ing the  stars.  This  is  no  fanciful  simile.  It  is 
simply  true  that  such  is  the  actual  appearance  of 
the  yolk  at  this  time ;  and  the  idea  cannot  but 
suggest  itself  to  the  mind,  that  the  thoughts 
which  have  been  embodied  in  the  universe  are 
recalled  here  within  the  little  egg,  presenting  a 
miniature  diagram  of  the  firmament.  This  is 
one  of  the  first  changes  of  the  yolk,  ending  by 
forming  regular  clusters,  with  a  sort  of  network 
of  albumen  between,  and  then  this  phase  of  the 
growth  is  complete. 

Now  the  clusters  of  the  yolk  separate,  and  next 
the  albumen  in  its  turn  concentrates  into  clusters, 


THE   OVAEIAN  EGG.  289 

and  the  dark  bodies,  which  have  been  till  now  the 
striking  points,  give  way  to  the  lighter  spheres  of 
albumen  between  which  the  clusters  are  scattered. 
Presently  the  whole  becomes  re-dissolved :  these 
stages  of  the  growth  being  completed,  this  little 
system  of  worlds  is  melted,  as  it  were  ;  but  while 
it  undergoes  this  process,  the  albuminous  spheres, 
after  being  dissolved,  arrange  themselves  in  con- 
centric rings,  alternating  with  rings  of  granules, 
around  the  Purkinjean  vesicle.  At  this  time  we 
are  again  reminded  of  Saturn  and  its  rings,  which 
seems  to  have  its  counterpart  here.  These  rings 
disappear,  and  now  once  more  out  of  the  yolk 
mass  loom  up  little  dots  as  minute  as  before  ;  but 
they  are  round  instead  of  angular,  and  those 
nearest  the  Purkinjean  vesicle  are  smaller  and 
clearer,  containing  less  of  oil  than  the  larger  and 
darker  ones  on  the  opposite  side.  From  this  time 
the  yolk  begins  to  take  its  color,  the  oily  cells 
assuming  a  yellow  tint,  while  the  albuminous 
cells  near  the  vesicle  become  whiter. 

Up  to  this  period  the  processes  in  the  different 
cells  seem  to  have  been  controlled  by  the  different 
character  of  the  substance  of  each ;  but  now  it 
would  seem  that  the  changes  become  more  in- 
dependent of  physical  or  material  influences,  for 
each  kind  of  cell  undergoes  the  same  process. 
They  all  assume  the  ordinary  cell  character,  with 
outer  and  inner  sac,  —  the  inner  sac  forming  on 

13  s 


290  THE   OVARIAN  EGG. 

the  side,  like  the  Purkinjean vesicle  itself;  but  it 
does  not  retain  this  position,  for,  as  soon  as  its 
wall  is  formed  and  it  becomes  a  distinct  body,  it 
floats  away  from  the  side  and  takes  its  place  in 
the  centre.  Next  there  arise  within  it  a  number 
of  little  bodies  crystalline  in  form,  and  which 
actually  are  wax  or  oil  crystals.  They  increase 
with  great  rapidity,  the  inner  sac  or  mesoblast 
becoming  sometimes  so  crowded  with  them  that 
its  shape  is  affected  by  the  protrusion  of  their 
angles.  This  process  goes  on  till  all  the  cells  are 
so  filled  by  the  mesoblast,  with  its  myriad  brood 
of  cells,  that  the  outer  sac  or  ectoblast  becomes  a 
mere  halo  around  it.  Then  every  mesoblast  con- 
tracts ;  the  contraction  deepens  till  it  is  divided 
across  in  both  directions,  separating  thus  into 
four  parts,  then  into  eight,  then  into  sixteen,  and 
so  on,  till  every  cell  is  crowded  with  hundreds  of 
minute  mesoblasts,  each  containing  the  indication 
of  a  central  dot  or  entoblast.  At  this  period  every 
yolk  cell  is  itself  like'  a  whole  yolk ;  for  each  cell 
is  as  full  of  lesser  cells  as  the  yolk-bag  itself. 

When  the  mesoblast  has  become  thus  infinitely 
subdivided  into  hundreds  of  minute  spheres,  the 
ectoblast  bursts,  and  the  new  generations  of  cells 
thus  set  free  collect  in  that  part  of  the  egg  where 
the  embryonic  disk  is  to  arise.  This  process  of 
segmentation  continues  to  go  on  downward  till 
the  whole  yolk  is  taken  in.  These  myriad  cells 


THE   OVARIAN  EGG.  291 

are,  in  fact,  the  component  parts  of  the  little  Turtle 
that  is  to  be.  They  will  undergo  certain  modi- 
fications, to  become  flesh-cells,  blood-cells,  brain- 
cells,  and  so  on,  adapting  themselves  to  the  dif- 
ferent organs  they  are  to  build  up  ;  but  they  have 
as  much  their  definite  and  appointed  share  in  the 
formation  of  the  body  now  as  at  any  later  stage 
of  its  existence. 

We  are  so  accustomed  to  see  life  maintained 
through  a  variety  of  complicated  organs,  that  we 
are  apt  to  think  this  the  only  way  in  which  it  can 
be  manifested  ;  and,  considering  how  entirely  the 
life  of  an  adult  animal  is  dependent  upon  the 
organs  through  which  it  is  sustained,  it  is  natu- 
ral that  we  should  be  deeply  impressed  by  their 
connection.  But  embryological  investigations 
have  taught  us  that  during  the  incipient  growth 
of  the  higher  animals  none  of  these  organs  exist, 
and  yet  the  principle  of  life  is  active,  and  even 
after  the  organs  are  formed,  they  cannot  act  at 
once,  most  of  them  being  enclosed  in  the  whole 
structure,  in  a  way  which  interferes  with  their 
later  functions.  In  the  little  Chicken,  for  in- 
stance, before  it  is  hatched,  the  lungs  cannot 
breathe,  for  they  are  surrounded  by  a  fluid  ;  the 
senses  are  inactive,  for  they  receive  no  impres- 
sions from  without,  and  all  those  functions  estab- 
lishing its  relations  with  the  external  world  lie 
dormant,  for  as  yet  they  are  not  needed.  But 


292  THE   OVARIAN  EGG. 

the  organs  are  there,  though,  as  we  have  seen  in 
the  Turtle's  egg,  they  were  not  there  at  the  be- 
ginning. How,  then,  are  they  formed?  We 
may  answer,  that  the  first  function  of  every  or- 
gan is  to  make  itself.  The  building  material  is, 
as  it  were,  provided  by  the  process  which  divides 
the  yolk  into  innumerable  cells,  and  by  the  grad- 
ual assimilation  and  modification  of  this  material 
the  organs  arise.  Before  the  lungs  breathe,  they 
make  themselves  ;  before  the  stomach  digests,  it 
makes  itself;  before  the  organs  of  the  senses  act, 
they  make  themselves  ;  before  the  brain  thinks, 
it  makes  itself.  In  a  word,  before  the  whole 
system  works,  it  makes  itself  out  of  the  elements 
given  by  the  formation  of  independent  eggs  :  its 
first  office  is  self-structure. 

At  the  period  described  above,  however,  when 
the  new  generations  of  cells  are  just  set  free  and 
have  taken  their  place  in  the  region  where  the 
new  being  is  to  develop,  nothing  is  to  be  seen  of 
the  animal  whose  life -is  beginning  there,  except 
the  filmy  disk  lying  on  the  surface  of  the  yolk. 
Next  come  the  layers  of  white  or  albumen  around 
the  egg,  and  last  the  shell  which  is  formed  from 
the  lime  in  the  albumen.  There  is  always  more 
or  less  of  lime  in  albumen,  and  the  hardening  of 
the  last  layer  of  white  into  shell  is  owing  only  to 
the  greater  proportion  of  lime  in  its  substance. 
In  the  layer  next  to  the  shell  there  is  enough  of 


THE   OVARIAN   EGG.  293 

lime  to  consolidate  it  slightly,  and  it  forms  a 
membrane ;  yet  the  white,  the  membrane,  and 
the  shell  have  all  the  same  quality,  except  that 
the  proportion  of  lime  is  more  or  less  in  the  dif- 
ferent layers. 

But,  as  I  have  said,  the  various  envelopes  of 
eggs,  the  presence  or  absence  of  a  shell,  and  the 
absolute  size  of  the  egg,  are  accessory  features, 
belonging  not  to  the  egg  as  egg,  but  to  the  spe- 
cial kind  of  being  from  which  the  egg  has  arisen, 
and  into  which  it  is  to  develop.  What  is  common 
to  all  eggs  and  essential  to  them  all  is  that  which 
corresponds  to  the  yolk  in  the  bird's  egg.  But 
their  later  mode  of  development,  the  degree  of 
perfection  acquired  by  the  egg  and  germ  before 
being  laid,  the  term  required  for  the  germ  to 
come  to  maturity,  as  well  as  the  frequency  and 
regularity  of  the  broods,  are  all  features  varying 
with  the  different  kinds  of  animals.  There  are 
those  that  lay  eggs  once  a  year,  at  a  particular 
season,  and  then  die  ;  so  that  their  existence  may 
be  compared  to  that  of  annual  plants,  undergo- 
ing their  natural  growth  in  a  season,  to  exist 
during  the  remainder  of  the  year  only  in  the 
form  of  an  egg  or  seed.  The  majority  of  Insects 
belong  to  this  category,  as  do  also  our  large 
Jelly-Fishes ;  many  others  have  a  slow  growth, 
extending  over  several  years,  during  which  they 
reach  their  maturity,  and  for  a  longer  or  shorter 


294  THE   OVARIAN  EGG. 

time  produce  broods  at  fixed  intervals ;  while 
others,  again,  reach  their  mature  state  very  rap- 
idly, and  produce  a  number  of  successive  genera- 
tions in  a  comparatively  short  time,  it  may  be 
in  a  single  season. 

I  do  not  intend  to  enter  upon  the  chapter  of 
special  differences  of  development  among  ani- 
mals, for  in  this  article  I  have  aimed  only  at 
showing  that  the  egg  lives,  that  it  is  itself  the 
young  animal,  and  that  the  vital  principle  is  active 
in  it  from  the  earliest  period  of  its  existence.  But 
I  would  say  to  all  young  students  of  Embryology 
that  their  next  aim  should  be  to  study  those  in- 
termediate phases  in  the  life  of  a  young  animal, 
when,  having  already  acquired  independent  exist- 
ence, it  has  not  yet  reached  the  condition  of  the 
adult.  Here  lies  an  inexhaustible  mine  of  valu- 
able information  unappropriated,  from  which,  as 
my  limited  experience  has  already  taught  me, 
may  be  gathered  the  evidence  for  the  solution  of 
the  most  perplexing  problems  of  our  science. 
Here  we  shall  find  the  true  tests  by  which  to  de- 
termine the  various  kinds  and  different  degrees 
of  affinity  which  animals  now  living  bear  not 
only  to  one  another,  but  also  to  those  that  have 
preceded  them  in  past  geological  times.  Here  we 
shall  find  not  a  material  connection  by  which 
blind  laws  of  matter  have  evolved  the  whole 
creation  out  of  a  single  germ,  but  the  clew  to  that 


THE   OVARIAN  EGG.  295 

intellectual  conception  which  spans  the  whole 
series  of  geological  ages,  and  is  perfectly  consist- 
ent in  all  its  parts.  In  this  sense  the  present 
will  indeed  explain  the  past,  and  the  young 
naturalist  is  happy  who  enters  upon  his  life  of 
investigation  now,  when  the  problems  that  were 
dark  to  all  his  predecessors  have  received  new 
light  from  the  sciences  of  Paleontology  and 
Embryology. 


296          EMBRYOLOGY  AND   CLASSIFICATION. 


CHAPTER    XYI. 

EMBRYOLOGY  AND   CLASSIFICATION. 

THE  investigation  of  the  structure  and  gradual 
growth  of  the  ovarian  egg  is  so  laborious  that 
it  will  be  many  years  before  we  can  hope  to 
have  a  complete  picture  of  all  its  phases.  The 
apparatus  required  for  the  task  is  very  compli- 
cated, and  a  long  training  is  necessary  merely 
to  prepare  the  student  for  the  use  of  his  instru- 
ments. A  superficial  familiarity  with  the  mi- 
croscope gives  no  idea  of  the  exhausting  kind 
of  labor  which  the  naturalist  must  undergo 
who  would  make  an  intimate  microscopic  study 
of  these  minute  living  spheres.  The  glance  at 
the  moon,  or  at  Jupiter's  satellites,  which  the 
chance  visitor  at  an  observatory  is  allowed  to 
take  through  the  gigantic  telescope,  reveals  to 
him  nothing  of  the  intense  concentrated  watch- 
ing by  which  the  observer  wins  his  higher  re- 
ward. The  nightly  vision  of  the  astronomer, 
revealing  myriad  worlds  in  the  vague  nebulous 
spaces  of  heaven,  is  not  for  him ;  he  must  take 
the  great  results  of  astronomy  for  granted,  "i 


EMBKYOLOGY  AND   CLASSIFICATION.  297 

no  man  capable  of  original  research  has  the 
time  to  prepare  for  the  uninitiated  the  attendant 
circumstances  essential  to  his  more  difficult  in- 
vestigations, or  to  train  their  eyes  to  see  what 
he  sees.  So  is  it  also  with  the  microscopic 
observer;  the  deeper  insight  he  has  gained  by- 
long  training  in  steadiness  of  hand  and  eye,  as 
well  as  in  the  concentration  of  intellect  that 
makes  the  brain  work  harmoniously  with  them, 
he  cannot  communicate.  He  may  interest  and 
amuse  his  friends  and  visitors  with  some  easy 
exhibition  of  specimens  under  the  microscope ; 
he  may  open  the  door  into  the  laboratory  of 
Nature,  but  he  cannot  invite  them  to  cross  the 
threshold  or  to  enter  in  with  him.  I  think 
people  are  not  generally  aware  of  the  difficulty 
of  microscopic  observation,  or  the  amount  of 
painful  preparation  required  merely  to  fit  the 
organs  of  sight  and  touch  for  the  work.  In  old 
times  men  prepared  themselves  with  fast  and 
vigil  for  entrance  into  the  temple  ;  and  Nature 
does  not  open  her  sanctuary  without  exacting 
due  penance  from  her  votaries.  It  seems  an 
easy  matter  for  a  man  to  sit  down  and  look  at 
objects  through  a  glass  which  enlarges  every- 
thing to  his  vision ;  but  there  are  subjects  of 
microscopic  research  so  obscure  that  the  student 
must  observe  a  special  diet  before  undertaking 
his  investigation,  in  order  that  even  the  beating 

13* 


298  EMBRYOLOGY  AND   CLASSIFICATION. 

of  his  arteries  may  not  disturb  the  steadiness 
of  his  gaze,  and  the  condition  of  his  nervous 
system  be  so  calm  that  his  whole  figure  will  re- 
main for  hours  in  rigid  obedience  to  his  fixed 
and  concentrated  gaze. 

After  these  remarks  I  trust  I  shall  not  be  mis- 
understood by  those  who  have  been  working  in 
the  field  of  microscopic  investigation,  and  for 
whose  persevering  devotion  no  one  can  feel  a 
deeper  reverence  than  I  do,  if  I  add  that  there 
is  as  yet  hardly  a  beginning  in  the  study  of  the 
egg  during  its  growth,  and  anterior  to  the  for- 
mation of  the  germ.  Since  Embryology  became 
a  science,  the  great  aim  of  students  in  that  de- 
partment* has  been  to  demonstrate  the  uniform 
structure  of  the  egg  in  all  animals,  and  investi- 
gators have  limited  their  observations  to  that 
stage  of  the  ovarian  egg  during  which  it  ap- 
pears in  all  animals  as  a  perfect  cell.  But  a 
new  field  now  opens  before  us,  requiring  a  care- 
ful survey  of  every  stage  of  growth  of  the  egg, 
from  its  first  formation  to  the  period  when  a 
well-defined  germ  is  developed.  The  growth  of 
the  egg  during  this  period  requires  to  be  studied 
as  minutely  through  all  its  changes,  and  in  the 
various  combinations  of  its  constitutive  elements, 
as  the  germ  itself  has  been  in  its  later  trans- 
formations. Here  again,  in  this  later  phase, 
another  field  presents  itself  equally  new  and 


EMBRYOLOGY  AND   CLASSIFICATION.  299 

full  of  promise.  Embryologists  have  generally 
considered  their  work  as  complete  when  they 
have  traced  the  new  being  to  a  point  at  which 
it  resembles  somewhat  any  of  the  members  of 
the  natural  group  to  which  it  belongs.  The 
process  by  which  the  gradual  completion  of  the 
whole  frame  is  attained  has  been  assumed  to 
be  one  of  little  interest,  hardly  deserving  the 
careful  scrutiny  of  the  embryologist ;  while  the 
zoologist  has  also  overlooked,  or  regarded  as  of 
little  importance,  the  differences  which  still  dis- 
tinguish the  young  from  the  adult,  even  after 
its  typical  characters  are  perfectly  distinct.  Yet 
naturalists  might  have  taken  a  hint  from  one 
class  of  Vertebrates  long  known  for  their  pecu- 
liar metamorphoses,  and  which  show  how  im- 
portant are  the  facts  to  be  learned  from  these 
early  stages  in  the  life  of  any  animal. 

More  than  a  century  ago  Roesel,  in  his  masterly 
work  on  the  Frogs  and  Toads  of  Germany,  repre- 
sented the  mode  of  reproduction  and  growth 
of  these  animals  with  a  remarkable  degree  of 
accuracy,  and  this  subject  has  since  been  traced 
with  additional  precision  and  minuteness  by  Rus- 
coni,  Von  Siebold,  and  Funke.  Notwithstanding 
this,  no  special  application  has  yet  been  made 
of  the  results  of  these  investigations  to  the  clas- 
sification of  these  animals,  beyond  the  general 
recognition  that  the  caudate  Batrachians,  with 


300  EMBRYOLOGY  AND   CLASSIFICATION. 

permanent  external  gills,  rank  lower  than  the 
Salamanders,  which  lose  their  gills  in  the  adult 
condition,  while  these  again  are  inferior  to  the 
Frogs  and  Toads,  in  which  the  tail  also  is  resorbed 
before  the  animal  completes  its  growth.  But 
the  comparison  of  the  higher  and  lower  Ba- 
trachians  should  not  stop  here.  A  more  exten- 
sive examination  shows  that  the  Tadpole  begins 
as  an  elongated  body,  not  only  without  legs, 
but  also  without  external  gills,  and  that  it  passes 
to  a  branchiate  condition,  with  more  or  less  de- 
veloped legs,  before  it  loses  the  gills,  while  there 
are  various  modes  of  development  of  the  limbs 
themselves,  —  various  phases  in  the  formation 
of  the  tail,  in  its  growth  and  resorption ;  vari- 
ous phases  also  in  the  formation  of  the  fingers, 
up  to  their  final  separation,  in  those  which  are 
destitute,  in  their  adult  condition,  of  any  web 
between  them.  This  gradation  is  so  complete, 
that  if  we  follow  all  the  phases  of  development 
of  the  several  representatives  of  this  class,  so 
common  everywhere  in  our  temperate  zone,  we 
cannot  fail  to  perceive  that  the  changes  these 
animals  undergo  during  their  growth  furnish  a 
complete  scale ;  and  if  we  now  compare  this 
scale  with  one  founded  upon  the  various  degrees 
of  structural  complication  in  the  adult  repre- 
sentatives of  the  class,  we  find  that  these  two 
series  agree  perfectly ;  so  that  Nature  herself 


EMBRYOLOGY  AND   CLASSIFICATION.  SOl 

furnishes  us  with  a  classification,  to  establish 
which  needs  no  arbitrary  interference  on  the 
part  of  the  naturalist,  since  it  is  founded  upon 
natural  evidence,  both  embryological  and  zoologi- 
cal. While  this  is  so  obvious  and  easy  among 
Batrachians,  I  have  no  doubt,  from  the  scanty 
investigations  I  have  already  made,  that  Embry- 
ology will  in  the  end  furnish  us  with  the  means 
of  recognizing  the  true  affinities  among  all  ani- 
mals, and  of  ascertaining  their  relative  standing 
and  normal  position  in  their  respective  classes 
with  the  utmost  degree  of  accuracy  and  precision ; 
but,  before  this  can  be  done,  we  must  be  as  fa- 
miliar with  the  different  stages  of  growth  of  the 
young  animals  of  all  classes  as  we  already  are 
with  those  of  Batrachians,  and  shall  probably 
have  to  push  our  researches  in  directions  not  yet 
dreamed  of. 

Without  entering  into  any  details  upon  this 
subject,  I  may  as  well  state  here,  that  among 
Fishes  I  have  lately  discovered  metamorphoses 
as  extensive  as  those  known  to  take  place  among 
Reptiles.  Pisciculture  being  carried  on  upon 
so  large  a  scale  in  some  parts  of  Europe,  it  is 
surprising  that  the  fact  should  not  have  been 
ascertained  long  ago.  This  is  perhaps  owing  to 
the  circumstance,  that  these  metamorphoses  be- 
gin after  the  hatching  of  the  young,  at  a  time 
when  they  are  apt  to  die  if  reared  in  close  con- 


302  EMBRYOLOGY  AND   CLASSIFICATION. 

fmement.  In  this  stage,  they  are,  moreover, 
generally  too  small  to  be  readily  seen  in  their 
natural  element.  Nevertheless,  this  is  the  most 
important  period  of  their  growth,  with  reference 
to  their  natural  affinities,  and  I  shall  take  an 
early  opportunity  to  show  how  our  young  fishes, 
aping  the  Gadoid  or  Blennioid  type  in  their  tran- 
sition period,  pass  gradually  into  that  of  Labroids 
and  Lophioids ;  how  fish  embryos,  resembling 
the  tadpoles  of  frogs  and  toads,  gradually  as- 
sume the  form  of  Cyprinodonts ;  how  Apods  are 
transformed  into  Jugulars  and  Abdominals,  and 
Malacopterygians  into  Acanthopterygians ;  and, 
finally,  how  a  natural  classification  of  the  fishe-s 
may  be  founded  upon  the  correspondence  which 
exists  between  their  embryonic  development  and 
their  structural  gradation. 

In  order  to  show  further  how  much  we  may  ex- 
pect from  such  investigations,  I  will  allude  briefly 
to  some  of  the  facts  with  which  my  own  studies 
have  thus  far  made  me  acquainted.  One  impor- 
tant truth  already  assumes  great  significance  in 
the  history  of  the  growth  of  animals ;  namely,  that 
whatever  the  changes  may  be  through  which  an 
animal  passes,  and  however  different  the  aspect 
of  these  phases  at  successive  periods  may  appear, 
they  are  always  limited  by  the  character  of  the 
type  to  which  the  animal  belongs,  and  never 
pass  that  boundary.  Thus,  the  Radiate  begins 


EMBKYOLOGY  AND   CLASSIFICATION.  303 

life  with  characters  peculiar  to  Radiates,  and 
ends  it  without  assuming  any  feature  of  a  higher 
type.  The  Mollusk  starts  with  a  character  es- 
sentially its  own,  in  no  way  related  to  the  Ra- 
diates, and  never  shows  the  least  tendency  to 
deviate  from  it,  either  in  the  direction  of  the 
Articulate  or  the  Vertebrate  types.  This  is 
equally  true  of  the  Articulates.  At  no  stage  of 
growth  are  their  young  homologous  to  those  of 
Mollusks  or  Radiates  any  more  than  to  those  of 
Vertebrates,  and  in  their  final  development  they 
stand  equally  isolated  from  all  others.  That  this 
is  emphatically  true  of  the  Vertebrates  has  already 
been  fully  recognized ;  and  the  facts  known  with 
reference  to  this  highest  type  of  the  Animal  King- 
dom might  have  served  as  a  warning  against  the 
loose  statements  still  current  concerning  the  so- 
called  infusorial  condition  of  the  young  Inver- 
tebrates. These  results  are  of  the  highest  impor- 
tance at  this  moment,  when  men  of  authority  in 
science  are  attempting  to  renew  the  theory  of  a 
general  transmutation  of  all  animals  of  the  higher 
types  out  of  the  lower  ones.  If  such  views  are 
ever  to  deserve  serious  consideration,  and  be  ac- 
knowledged as  involving  a  scientific  principle,  it 
will  only  be  when  their  supporters  shall  have 
shown  that  the  fundamental  plans  of  structure 
characteristic  of  the  primary  groups  of  the  Ani- 
mal Kingdom  are  transmutable,  or  pass  into  one 


304  EMBRYOLOGY  AND   CLASSIFICATION. 

another,  and  that  their  different  modes  of  de- 
velopment may  lead  from  one  to  the  other. 
Thus  far  Embryology  has  not  recorded  one  fact 
on  which  to  base  such  doctrines. 

In  Radiates,  as  soon  as  the  young  is  formed, 
it  is  a  spheroidal,  radiated  animal,  exhibiting 
from  the  beginning,  in  all  the  three  classes  of 
this  primary  division,  —  Polyps,  Acalephs,  and 
Echinoderms,  —  the  general  plan  of  structure  so 
characteristic  of  the  Radiate  type,  and  so  distinct 
from  all  others.  Let  us  first  see  what  inference 
may  be  drawn  from  the  development  of  the  lower 
representatives  of  this  type ;  even  though  I  can 
only  allude  here  very  generally  to  facts  which 
could  not  be  stated  more  at  length  without  a 
great  deal  of  illustration  and  detail.  The  young 
Polyp  reaches  its  mature  condition  through  a 
succession  of  changes,  which,  when  compared 
with  the  structural  complication  of  the  adult 
representatives  of  the  different  orders  in  this 
same  class,  promise  'to  furnish  better  data  for  the 
classification  of  these  animals  than  have  ever 
been  obtained  heretofore.  The  various  modes 
of  increase  observed  among  Astra3ans,  and  espe- 
cially among  Fungidae,  already  show  that  the 
families  in  which  independent  animals  complete 
their  growth,  without  forming  compound  com- 
munities, are  inferior  to  the  compound  ones ; 
while  those  in  which  one  diameter  prevails  over 


EMBKYOLOGY   AND   CLASSIFICATION.  305 

the  other  are  superior  to  those  with  circular  out- 
lines. The  Maiiicina,  with  its  convoluted  trench- 
es, is,  in  its  earlier  condition,  a  perfectly  cir- 
cular hydra-like  simple  Polyp;  and  the  young 
Herpolitha  is  also  a  simple  circular  animal,  so 
closely  resembling  a  young  Fungia  that  it 
might  be  referred  to  the  same  genus.  I  have 
no  doubt  that,  when  the  embryonic  history 
of  the  young  Madrepore  is  fully  understood,  it 
will  be  found  that  this  group  also  resembles  the 
young  Astraea  at  first,  though  it  stands  so  much 
above  it  in  its  adult  condition.  In  truth,  all 
these  higher  representatives  of  the  class  of  Polyps 
resemble  the  lower  ones  in  their  earliest  state, 
starting  from  a  point  common  to  all,  and  passing 
through  phases  which  are  permanent  and  final 
for  the  lower  forms,  but  are  only  transient  stages 
in  the  development  of  the  higher  ones. 

I  have  dwelt  so  much  upon  the  Embryology  of 
the  Acalephs  in  another  chapter,  that  I  need  only 
remind  my  readers  here  that  this  class  also  has  a 
common  starting-point,  exhibiting  a  remarkable 
uniformity  among  the  young,  which  extends  even 
to  the  Ctenophora3,  the  affinities  of  which  have 
been,  and  still  are,  the  subject  of  controversy 
among  naturalists.  In  this  class  also,  the  differ- 
ent phases  of  development  furnish  the  best  basis 
for  a  classification  of  its  representatives. 

Until  very  recently  it  had  been  believed  that 


306  EMBRYOLOGY  AND   CLASSIFICATION. 

the  highest  class  in  this  division  —  the  Echino- 
derms  —  made  an  exception  to  this  rule,  and  did 
not  agree  with  the  other  Radiates  in  its  mode  of 
development.  Johannes  Miiller,  one  of  the  most 
eminent  investigators  of  modern  times,  in  a  long 
series  of  memorable  papers  upon  the  Embryology 
of  Radiates,  has  maintained  that  the  larval  con- 
dition of  the  young  Echinoderm,  so  far  from  being 
homologous  with  the  early  stages  of  development 
in  the  other  classes,  is  essentially  bilateral.  It  is 
true  that  there  is  in  many  of  the  Radiates  some- 
thing akin  to  a  bilateral  symmetry,  though  it  is 
always  subordinate  to  the  prevailing  idea  of  radi- 
ation in  the  plan.  This  tendency  is  already  quite 
perceptible  in  the  highest  order  of  the  Acalephs, 
the  Ctenophorae,  and  becomes  still  more  so  in 
some  representatives  of  the  class  of  Echinoderms, 
the  highest  in  this  type.  The  resemblance  of  the 
larvae  of  the  Echinoderms  to  the  Ctenophorae  had 
not  escaped  my  notice  ;  but  during  the  past  year 
my  son  has  shown  conclusively,  in  a  series  of 
microscopic  investigations  not  yet  published,  that 
they  are  as  truly  radiated  as  the  most  circular  or 
spheroidal  of  the  type.  The  further  growth  of 
the  young  Echinoderms,  from  the  young  Comatula 
(as  far  as  its  history  is  known  in  its  pentacrinal 
condition)  to  the  gradual  transformation  of  the 
common  Star-Fish,  with  its  undivided  circular 
outline,  with  its  two  rows  of  simple  ambulacral 


EMBRYOLOGY  AND   CLASSIFICATION.  307 

suckers  without  a  disk  at  their  end,  and  to  the 
various  Echinoids  and  Holothurians,  the  early 
phases  of  whose  growth  are  described  by  J.  Miil- 
ler,  shows  plainly  that  the  metamorphosis  of  the 
Comatula  furnishes  a  scale  for  the  classification 
of  all  the  Crinoids  of  past  ages,  just  as  that  of  the 
common  Five-Finger  (Asterias)  gives  the  key  to 
the  relative  standing  of  all  the  families  of  Star- 
Fishes,  the  more  circular  or  pentagonal  forms  of 
which  are  respectively  inferior  to  their  star-shaped 
allies,  those  with  two  rows  of  suckers  inferior  to 
those  with  four,  and  those  with  simple  ambulacra 
inferior  to  those  in  which  the  ambulacra  have 
a  disk-shaped  extremity. 

The  beautiful  investigations  of  Miiller  have 
made  us  acquainted  with  the  young  of  several 
families  of  the  order  of  Echini  or  Sea-Urchin,  in- 
cluding the  Spatangoids,  so  different  with  their 
oblong  form  and  eccentric  mouth  from  the  cir- 
cular Sea-Urchin,  with  its  central  mouth.  Yet 
the  Spatangoid  in  its  earlier  stages  is  spheroidal, 
like  the  young  Echinus ;  and  the  ambulacral 
apparatus,  so  highly  differentiated  in  its  vertical 
extension  in  the  adult  Spatangoid,  is  as  simple  in 
the  young  as  in  the  Echinus.  The  adult  Spatan- 
goid is  covered  with  innumerable  hair-like  spines, 
while  the  young  bears  only  a  few  large  rods,  re- 
sembling even  more  those  of  a  Cidaris  than  those 
of  an  Echinus.  We  may,  indeed,  fairly  say,  that 


308  EMBRYOLOGY  AND   CLASSIFICATION. 

the  successive  changes  of  the  higher  Echinoids 
make  us  acquainted  with  a  series  of  transfor- 
mations which  have  their  counterparts,  not  only 
in  the  different  families  of  the  order  as  ranked 
one  above  the  other,  but  also  in  the  order  of  suc- 
cession of  these  Radiates  in  past  geological  times. 
Even  among  the  Holothurians,  imperfectly  as 
their  development  is  known,  it  already  appears, 
upon  embryonic  data,  that  those  without  external 
ambulacra  are  inferior  to  those  which  have  them, 
since  the  latter  are  destitute  of  these  organs  in 
their  earlier  stages  of  growth.  Notwithstanding 
the  direct  bearing  of  these  embryological  facts 
upon  the  classification  of  the  Echinoderms,  it  is 
surprising  that  no  attention  has  thus  far  been  paid 
to  the  subject ;  the  eminent  physiologist  himself, 
to  whom  we  owe  so  large  a  share  of  our  knowl- 
edge of  the  facts  above  referred  to,  has  failed  to 
perceive  their  significance  in  this  connection. 

It  would  require  a  discussion  of  facts  not  yet 
sufficiently  familiar  'even  to  naturalists,  were  I  to 
attempt  a  similar  comparison  of  the  successive 
stages  of  growth  of  the  Mollusks  with  the  relative 
standing  of  the  different  members  of  their  respec- 
tive classes ;  and  yet,  as  I  have  by  my  own  in- 
vestigations reached  a  synthesis  which  enables 
me  to  discuss  the  question  in  its  most  general 
bearing,  I  beg  leave  to  submit  here  a  few  state- 
ments, the  full  demonstration  of  which  may  be 


EMBRYOLOGY  AND   CLASSIFICATION.  309 

furnished  hereafter.  In  many  marine  slugs  ana 
univalve  shells  the  development  of  the  young  has 
been  traced  again  and  again  ;  and  their  great  re- 
semblance among  themselves,  during  the  earlier 
phases  of  their  growth,  has  already  attracted  the 
attention  of  all  zoologists.  This  is  the  more  re- 
markable when  taken  in  connection  with  the 
extraordinary  external  difference  in  the  appear- 
ance of  the  adult.  The  young  resemble  a  some- 
what compressed  oblong  bag,  supporting  a  broad 
crescent-shaped  veil,  stretching  evenly  in  every 
direction  on  one  side  of  the  bag,  and  provided 
around  its  edge  with  powerful  vibratile  cilia,  by 
the  agency  of  which  these  small  animals  rotate  in 
the  water  with  great  activity.  In  this  condition 
the  bag  is  protected  by  a  very  thin  transparent 
shell,  existing  even  in  those  which  are  destitute 
of  shell  both  in  the  earlier  and  later  stages  of 
their  existence,  being  unprovided  with  any  such 
covering  at  first,  and  dropping  it  before  they  com- 
plete their  growth.  The  young  of  the  Sea-Slugs, 
which,  with  a  large  number  of  our  marine  Gas- 
teropods  and  Pteropods,  have  been  very  carefully 
observed,  may  give  an  idea  of  the  younger  stages 
of  all  Mollusks  ;  for,  different  as  may  be  the 
appearance  of  the  young  Cephalopod  at  some 
periods  of  its  life,  it  is  not  difficult,  nevertheless, 
to  trace  their  homology,  and  even  their  close 
resemblance,  at  certain  periods,  to  the  young  of 


310  EMBRYOLOGY   AND   CLASSIFICATION. 

the  Gasteropods,  described  above.  I  have  satis- 
fied myself  .of  this  fact  while  studying  the  trans- 
formation of  the  young  of  our  common  Squid 
(Loligo  illecebrosa) .  Nor  are  the  young  of  our 
common  Bivalves,  and  even  those  of  our  Ascidians 
(the  so-called  soft-shelled  Clams)  or  of  the  Bryo- 
zoa,  essentially  different ;  while  a  closer  compari- 
son of  the  condition  of  the  young  of  the  two  latter 
groups,  during  the  stage  when  they  swarm  in  the 
water  as  free  floating  animals,  will  readily  show 
that  they  bear  a  similar  relation  to  the  young 
Gasteropods  and  the  young  Cephalopods  as  the 
Echinoderm  Iarva3  bear  to  the  young  swarming 
Acalephs  or  the  young  Polyps.  In  the  later 
phases  of  their  advance  toward  a  mature  con- 
dition they  constantly  recall  the  appearance  and 
form  of  other  representatives  of  their  respective 
classes,  so  that  even  an  imperfect  acquaintance 
with  this  subject  leads  to  the  inference  that  there 
probably  exists  between  the  successive  stages  of 
growth  of  the  Mollusk  the  same  correspondence 
with  the  different  members  of  their  respective 
classes,  in  their  natural  gradation,  as  has  already 
been  observed  in  the  other  types.  A  comparison 
of  the  young  of  many  Gasteropods,  which,  like 
Natica,  Pyrula,  Buccinum,  and  Purpura,  under- 
go their  early  development  in  solid  egg-cases, 
has  already  furnished  very  interesting  results  ; 
and  collectors  cannot  be  too  careful  in  gather- 


EMBKYOLOGY  AND   CLASSIFICATION.  311 

ing  these  specimens,  and  making  constant  efforts 
to  ascertain  by  what  Mollusks  they  are  laid. 
The  fact  that  among  Acephala  the  bivalve  shells, 
which  have  two  transverse  bundles  of  muscles  in 
their  adult  condition,  have  only  one  in  earlier 
life,  furnishes  a  satisfactory  evidence  of  the  lower 
standing  of  the  Monomyaria  when  compared  to 
the  Dimyaria;  and  a  closer  investigation  leaves 
no  doubt  that  the  one  large  transverse  muscle 
of  the  Oyster  corresponds  to  the  posterior  muscle 
of  the  Clam  (Mactra  or  My  a).  Again,  the  prev- 
alence of  the  vertical  diameter  over  the  longi- 
tudinal and  the  transverse  in  the  young,  while 
later  the  longitudinal  diameter  takes  the  lead, 
affords  valuable  information  respecting  the  rela- 
tive standing  of  short-bodied  or  rounded  Bivalves 
in  comparison  with  their  more  elongated  allies. 
And  this  is  in  accordance  with  the  inferior  posi- 
tion of  the  Brachiopods  and  Bryozoa.  But  the 
classification  of  Mollusks  is  too  little  advanced 
as  regards  the  relative  standing  of  their  numer- 
ous families  to  allow  a  more  direct  comparison 
at  present. 

In  the  type  of  Articulates  the  difficulties  are 
of  another  kind.  The  extraordinary  number  of 
representatives  in  the  classes  of  this  type  renders 
a  comprehensive  view  of  their  respective  stand- 
ing particularly  difficult ;  and  yet,  if  we  leave  out 
of  sight  the  minor  divisions,  and  keep  in  mind 


312  EMBRYOLOGY   AND   CLASSIFICATION. 

only  the  most  prominent  ones,  the  correspond- 
ence between  the  phases  of  growth  of  the  young 
and  the  relative  position  of  the  different  groups 
of  adults  in  their  respective  classes  is  very  obvi- 
ous. The  worm-like  character  of  the  larval  con- 
dition of  Insects  has  been  noticed  by  all  ento- 
mologists, and  the  crustacean  features  of  their 
pupa  are  equally  apparent.  Neither  can  the  an- 
alogy be  overlooked  between  the  Centipedes  and 
the  Worms,  or  that  between  the  Spiders  and  Crus- 
tacea. We  have  here  the  fullest  evidence  that 
while  the  highest  Insects  recall  in-  their  earlier 
condition  the  permanent  character  of  the  adult 
representatives  of  the  lower  classes  in  their  type, 
those  Insects  which  in  their  class  occupy  a  middle 
and  lower  position,  such  as  the  Spiders  and  Cen- 
tipedes, also  correspond  to  the  lower  classes  of  the 
same  type.  Any  one  familiar  with  the  transfor- 
mations of  Butterflies,  and  the  successive  phases 
of  their  final  development,  must  have  perceived 
that,  even  while  unfolding  its  wings,  in  one  sin- 
gle act  preliminary  to  taking  its  flight,  the  But- 
terfly truly  recalls  the  form  and  mode  of  folding 
the  wings  peculiar  to  the  Moths  and  Sphinxes. 
It  is  therefore  particularly  desirable  that  all 
these  changes  should  not  only  be  separately  de- 
scribed, as  they  have  been  successively  observed 
in  different  Insects,  but  minutely  compared  with 
one  another,  so  as  to  establish  with  more  pre- 


-       EMBRYOLOGY  AND   CLASSIFICATION.  313 

cision  the  correspondence  of  all  their  different 
conditions.  In  this  direction  there  is  a  boundless 
field  open  to  the  researches  of  young  naturalists. 
In  the  class  of  Crustacea  enough  is  already 
known  to  establish  a  correspondence  between 
the  young  of  the  higher  members  of  the  class 
and  the  adults  of  its  lower  members ;  and  the 
comparison  may  here  be  extended  with  remark- 
able precision  to  the  fossils  of  past  ages,  since 
representatives  of  this  class  are  known  from  the 
earliest  geological  epochs  in  which  animals  ex- 
isted at  all  to  the 'present  time.  The  class  of 
worms  has  of  late  attracted  so  much  attention, 
and  so  many  of  them  have  been  studied  during 
their  transformation,  that,  were  these  animals 
more  generally  known,  I  could  adduce  striking 
instances  of  this  correspondence  between  the 
younger  stages  of  growth  in  the  higher  mem- 
bers of  the  class  and  the  adult  forms  of  its  lower 
representatives.  But  I  will  not  enter  into  these 
details,  as  I  have  no  vernacular  names  by  which 
I  could  designate  them  intelligibly,  and  for  pro- 
fessional naturalists  this  allusion  is  sufficient. 
They  will  remember  that  the  highest  worms  so 
remarkable  for  the  various  locomotive  and  respi- 
ratory appendages  on  their  sides,  are,  in  their 
earlier  phases,  as  destitute  of  these  appendages 
as  are  the  lowest  members  of  the  class  in  their 
adult  condition. 

14 


314  EMBRYOLOGY  AND    CLASSIFICATION. 

If  we  now  pass  to  the  highest  type  of  the  Ani- 
mal Kingdom,  the  Vertebrates,  there  is  no  lack  of 
evidence  to  show  the  identity  in  their  mode  of 
development,  as  well  as  the  striking  resemblance 
of  the  young  in  their  earliest  stages  of  growth. 
The  young  Fish,  the  young  Reptile,  the  young 
Bird,  the  young  Mammal,  resemble  one  another 
to  an  astonishing  degree,  while  they  have  not  one 
feature  in  their  mode  of  growth  which  recalls 
either  the  Articulate,  the  Mollusk,  or  the  Radiate. 
It  is,  therefore,  not  true,  though  so  often  stated, 
that  in  their  development  the  higher  animals 
pass  successively  through  the  condition  of  all  the 
lower  ones ;  while  it  is  emphatically  true  that  in 
each  of  the  four  great  branches  of  the  Animal 
Kingdom  there  is  a  common  mode  of  develop 
ment.  It  is  equally  true  that  in  certain  features 
the  higher  classes  of  each  branch  in  their  younger 
condition  recall  the  characteristic  features  of  the 
lower  ones,  though  each  class  has  its  own  struc- 
tural character,  and  early  diverges  from  the  com- 
mon starting-point.  One  single  case  may  suffice 
to  demonstrate  this  general  statement.  When 
the  young  Skate  begins  to  form  upon  the  large 
yolk  of  its  egg,  it  has  an  oblong  form,  somewhat 
club-shaped,  the  broader  end  representing  the 
head,  while  the  tapering  end  is  the  tail.  It  is 
early  surrounded  by  a  network  of  bloodvessels 
circumscribed  upon  the  yolk  by  a  circular  vein. 


EMBRYOLOGY  AND   CLASSIFICATION.  315 

In  this  condition  it  closely  resembles  the  young 
Snake  as  represented  by  Rathke,  or  the  young 
Bird  as  represented  by  Pander,  or  the  young 
Rabbit  as  represented  by  Bischoff,  and  the  inex- 
perienced student  of  Embryology  would  find  it 
difficult  to  detect  any  character  by  which  these 
different  embryos  could  be  referred  to  their  re- 
spective classes  among  Vertebrates ;  for  nothing 
indicates  in  them  as  yet  the  Fish  or  the  Reptile, 
the  Bird  or  the  Mammal.  But  as  they  increase 
in  size  and  complication  of  structure,  the  young 
Skate  becoming  prominent  above  the  yolk  from 
which  it  is  nourished,  it  may  be  perceived  that, 
while  it  retains  its  primitive  connection  with  the 
yolk,  through  the  enlarged  vessels  first  observed, 
its  body  remains  exposed  above  it,  while  in  the 
other  three  the  body  becomes  enclosed  in  a  bag 
which  gradually  grows  out  of  its  own  lower  mar- 
gin, and,  bending  over  the  back,  closes  upon  it 
to  form  a  protecting  envelope,  the  amnios,  while 
another  bag,  the  allantois,  now  extends  from  the 
lower  side,  covered  with  vessels,  which  increase  in 
number  and  extent  as  the  bag  grows  larger,  while 
at  the  same  time  the  vessels  of  the  yolk  and  the 
yolk  itself  are  gradually  drawn  into  the  body. 
This  new  bag,  with  its  innumerable  vessels,  folds 
also  in  every  direction  over  the  young  already  en- 
closed in  its  first  bloodless  envelope,  and  so  forms 
a  second  protecting  sac.  From  this  time  forward 


316  EMBRYOLOGY  AND   CLASSIFICATION. 

the  Fish  can  no  longer  be  confounded  with  the 
young  Bird  or  Reptile  or  Mammal,  and  the  blood- 
vessels of  the  latter  will  soon  enter  into  such  con- 
nection with  the  parent  as  to  distinguish  it  also 
from  the  young  Bird  or  Reptile  which  forms  no 
such  connection.  I  will  not  pursue  this  trans- 
formation farther  in  all  its  details,  which  would 
require  numerous- figures  to  be  well  understood, 
but  briefly  allude  to  a  few  facts  proving  still  more 
clearly  the  unity  of  plan  prevailing  throughout 
the  whole  Vertebrate  type. 

The  young  Skate  up  to  the  period  already  de- 
scribed does  not  differ  from  the  young  Shark ; 
but  when  the  fins  make  their  appearance,  though 
exactly  the  same  at  first  in  both  these  animals, 
one  pair  in  the  Skate  presently  grows  larger 
than  the  others,  expanding  upon  the  sides  of  the 
body  and  expending  towards  the  tail  and  towards 
the  front  of  the  head.  Thus  the  young  Skate, 
as  it  advances  in  life,  leaves  behind  the  Shark 
character,  common  to  both  in  their  younger 
state,  but  permanent  only  in  the  Shark,  in  which 
the  fins  undergo  no  such  change.  This  shows 
beyond  a  doubt  that  the  family  of  Skates  is  su- 
perior to  that  of  Sharks,  —  an  inference  which 
is  confirmed  by  the  order  of  their  succession 
upon  earth,  the  Shark  family  having  preceded 
that  of  the  Skates,  in  geological  times.  But  it  is 
not  only  among  the  lower  groups  that  such  cor- 


EMBRYOLOGY  AND   CLASSIFICATION.  317 

respondences  may  be  traced.  The  resemblance 
of  an  adult  Skate,  especially  in  the  configuration 
of  the  face,  the  form  of  the  mouth,  the  position 
of  the  nostrils,  the  arrangement  of  the  gills,  to 
some  of  the  earlier  conditions  in  the  growth  of 
the  young  Mammal,  not  excepting  the  human 
family,  is  equally  striking.  No  one  can  fail  to  be 
impressed  with  this  resemblance  who  compares 
the  head  of  an  embryo  quadruped,  looking  at  it 
in  front  face,  with  the  adult  Skate.* 

Indeed,  modern  Embryology  leads  at  once  to 
the  consideration  of  the  most  occult  problem,  as 
to  the  origin  of  animals,  suggested  by  these  com- 
parisons. What  do  these  resemblances  mean, 
from  some  of  which  we  shrink  as  unnatural  and 
even  revolting  ?  If  we  put  a  material  interpre- 
tation upon  them,  and  believe  that  even  Man 
himself  has  been  gradually  developed  out  of  a 
Fish,  they  are  repugnant  to  our  better  nature. 
But  looked  at  in  their  intellectual  significance, 
they  truly  reveal  the  unity  of  the  organic  con- 
ception of  which  Man  himself  is  a  part,  and  mark 
not  only  the  incipient  steps  in  its  manifestation, 
but  also,  with  equal  distinctness,  every  pha,se  in 
its  gradual  realization.  They  mean  that  when 
the  first  Fish  was  called  into  existence,  the  Ver- 

*  Let  any  one  who  doubts  the  truth  of  this  statement  as  re- 
gards the  human  embryo  compare  the  figures  of  the  latter,  pub- 
lished by  Ecker,  in  the  Icones  Physiologicce,  with  any  adult  Skate, 


318  EMBRYOLOGY   AND   CLASSIFICATION. 

tebrate  type  existed  as  a  whole  in  the  creative 
thought,  and  the  first  expression  of  it  embraced 
potentially  all  the  organic  elements  of  that  type, 
up  to  Man  himself.  To  me  the  fact  that  the 
embryonic  form  of  the  highest  Vertebrate  recalls 
in  its  earlier  stage  the  first  representatives  of  its 
type  in  geological  times  and  its  lowest  repre- 
sentatives at  the  present  day,  speaks  only  of  an 
ideal  relation,  existing,  not  in  the  things  them- 
selves, but  in  the  mind  that  made  them.  It  is 
true  that  the  naturalist  is  sometimes  startled  at 
these  transient  resemblances  of  the  young  among 
the  higher  animals  in  one  type  to  the  adult  con- 
dition of  the  lower  animals  in  the  same  type ; 
but  it  is  also  true  that  he  finds  each  one  of  the 
primary  divisions  of  the  Animal  Kingdom  bound 
to  its  own  norm  of  development,  which  is  abso- 
lutely distinct  from  that  of  all  the  others ;  it  is 
also  true,  that,  while  he  perceives  corresponden- 
ces between  the  early  phases  of  the  higher  animals 
and  the  mature  state  of  the  lower  ones,  he  never 
sees  any  one  of  them  diverge  in  the  slightest 
degree  from  its  own  structural  character,  —  never 
sees  the  lower  rise  by  a  shade  beyond  the  level 
which  is  permanent  for  the  group  to  which  it 
belongs,  —  never  sees  the  higher  ones  stop  short 
of  their  final  aim,  either  in  the  mode  or  the 
extent  of  their  transformation.  I  cannot  repeat 
too  emphatically,  that  there  is  not  a  single  fact 


EMBRYOLOGY  AND   CLASSIFICATION.  319 

in  Embryology  to  justify  the  assumption  that  the 
laws  of  development,  now  known  to  be  so  precise 
and  definite  for  every  animal,  have  ever  been 
less  so,  or  have  ever  been  allowed  to  run  into 
each  other.  The  philosopher's  stone  is  no  more 
to  be  found  in  the  organic  than  the  inorganic 
world  ;  and  we  shall  seek  as  vainly  to  transform 
the  lower  animal  types  into  the  higher  ones  by 
any  of  our  theories,  as  did  the  alchemists  of  old 
to  change  the  baser  metals  into  gold. 


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